diff --git a/ble/CallChainOfFunctionPointersWithContext.h b/ble/CallChainOfFunctionPointersWithContext.h
index 3d5ff7d..fcda1c5 100644
--- a/ble/CallChainOfFunctionPointersWithContext.h
+++ b/ble/CallChainOfFunctionPointersWithContext.h
@@ -18,6 +18,7 @@
 
 #include <string.h>
 #include "FunctionPointerWithContext.h"
+#include "SafeBool.h"
 
 
 /** Group one or more functions in an instance of a CallChainOfFunctionPointersWithContext, then call them in
@@ -56,7 +57,7 @@
  */
 
 template <typename ContextType>
-class CallChainOfFunctionPointersWithContext {
+class CallChainOfFunctionPointersWithContext : public SafeBool<CallChainOfFunctionPointersWithContext<ContextType> > {
 public:
     typedef FunctionPointerWithContext<ContextType> *pFunctionPointerWithContext_t;
 
@@ -97,6 +98,49 @@ public:
         return common_add(new FunctionPointerWithContext<ContextType>(tptr, mptr));
     }
 
+    /** Add a function at the front of the chain.
+     *
+     *  @param func The FunctionPointerWithContext to add.
+     */
+    pFunctionPointerWithContext_t add(const FunctionPointerWithContext<ContextType>& func) {
+        return common_add(new FunctionPointerWithContext<ContextType>(func));
+    }
+
+    /** 
+     * Detach a function pointer from a callchain
+     * 
+     * @oaram toDetach FunctionPointerWithContext to detach from this callchain
+     * 
+     * @return true if a function pointer has been detached and false otherwise
+     */ 
+    bool detach(const FunctionPointerWithContext<ContextType>& toDetach) { 
+        pFunctionPointerWithContext_t current = chainHead;
+        pFunctionPointerWithContext_t previous = NULL;
+
+        while (current) {
+            if(*current == toDetach) { 
+                if(previous == NULL) {
+                    if(currentCalled == current) { 
+                        currentCalled = NULL;
+                    }
+                    chainHead = current->getNext();
+                } else {
+                    if(currentCalled == current) { 
+                        currentCalled = previous;
+                    }
+                    previous->chainAsNext(current->getNext());
+                }
+                delete current;
+                return true;
+            }
+
+            previous = current;
+            current = current->getNext();
+        }
+
+        return false;
+    }
+
     /** Clear the call chain (remove all functions in the chain).
      */
     void clear(void) {
@@ -115,16 +159,56 @@ public:
     }
 
     /** Call all the functions in the chain in sequence
-     * @Note: The stack frames of all the callbacks within the chained
-     *        FunctionPointers will stack up. Hopefully there won't be too many
-     *        chained FunctionPointers.
      */
     void call(ContextType context) {
-        if (chainHead) {
-            chainHead->call(context);
+        ((const CallChainOfFunctionPointersWithContext*) this)->call(context);
+    }
+
+    /**
+     * @brief same as above but const 
+     */
+    void call(ContextType context) const {
+        currentCalled = chainHead;
+
+        while(currentCalled) { 
+            currentCalled->call(context);
+            // if this was the head and the call removed the head
+            if(currentCalled == NULL) { 
+                currentCalled = chainHead;
+            } else {
+                currentCalled = currentCalled->getNext();
+            }
         }
     }
 
+    /**
+     * @brief same as above but with function call operator
+     * \code
+     * 
+     * void first(bool);
+     * void second(bool);
+     * 
+     * CallChainOfFunctionPointerWithContext<bool> foo;
+     * 
+     * foo.attach(first);
+     * foo.attach(second);
+     * 
+     * // call the callchain like a function
+     * foo(true);
+     * 
+     * \endcode
+     */
+    void operator()(ContextType context) const {
+        call(context);
+    }
+
+    /**
+     * @brief bool conversion operation
+     */
+    bool toBool() const {
+        return chainHead != NULL;
+    }
+
 private:
     pFunctionPointerWithContext_t common_add(pFunctionPointerWithContext_t pf) {
         if (chainHead == NULL) {
@@ -139,6 +223,11 @@ private:
 
 private:
     pFunctionPointerWithContext_t chainHead;
+    // iterator during a function call, this has to be mutable because the call function is const.
+    // Note: mutable is the correct behaviour here, the iterator never leak outside the object.
+    // So the object can still be seen as logically const even if it change its internal state
+    mutable pFunctionPointerWithContext_t currentCalled;
+
 
     /* Disallow copy constructor and assignment operators. */
 private:
diff --git a/ble/DiscoveredCharacteristic.h b/ble/DiscoveredCharacteristic.h
index 1ff67b8..583a8de 100644
--- a/ble/DiscoveredCharacteristic.h
+++ b/ble/DiscoveredCharacteristic.h
@@ -83,6 +83,8 @@ public:
      */
     ble_error_t read(uint16_t offset = 0) const;
 
+    ble_error_t read(uint16_t offset, const GattClient::ReadCallback_t& onRead) const;
+
     /**
      * Perform a write without response procedure.
      *
@@ -135,6 +137,11 @@ public:
      */
     ble_error_t write(uint16_t length, const uint8_t *value) const;
 
+    /** 
+     * Same as above but register the callback wich will be called once the data has been written
+     */
+    ble_error_t write(uint16_t length, const uint8_t *value, const GattClient::WriteCallback_t& onRead) const;
+
     void setupLongUUID(UUID::LongUUIDBytes_t longUUID) {
         uuid.setupLong(longUUID);
     }
diff --git a/ble/FunctionPointerWithContext.h b/ble/FunctionPointerWithContext.h
index 5fb6e29..02b07a6 100644
--- a/ble/FunctionPointerWithContext.h
+++ b/ble/FunctionPointerWithContext.h
@@ -18,14 +18,16 @@
 #define MBED_FUNCTIONPOINTER_WITH_CONTEXT_H
 
 #include <string.h>
+#include "SafeBool.h"
 
 /** A class for storing and calling a pointer to a static or member void function
  *  that takes a context.
  */
 template <typename ContextType>
-class FunctionPointerWithContext {
+class FunctionPointerWithContext : public SafeBool<FunctionPointerWithContext<ContextType> > {
 public:
     typedef FunctionPointerWithContext<ContextType> *pFunctionPointerWithContext_t;
+    typedef const FunctionPointerWithContext<ContextType> *cpFunctionPointerWithContext_t;
     typedef void (*pvoidfcontext_t)(ContextType context);
 
     /** Create a FunctionPointerWithContext, attaching a static function.
@@ -33,7 +35,7 @@ public:
      *  @param function The void static function to attach (default is none).
      */
     FunctionPointerWithContext(void (*function)(ContextType context) = NULL) :
-        _function(NULL), _caller(NULL), _next(NULL) {
+        _memberFunctionAndPointer(), _caller(NULL), _next(NULL) {
         attach(function);
     }
 
@@ -48,6 +50,17 @@ public:
         attach(object, member);
     }
 
+    FunctionPointerWithContext(const FunctionPointerWithContext& that) : 
+        _memberFunctionAndPointer(that._memberFunctionAndPointer), _caller(that._caller), _next(NULL) {
+    }
+
+    FunctionPointerWithContext& operator=(const FunctionPointerWithContext& that) {
+        _memberFunctionAndPointer = that._memberFunctionAndPointer;
+        _caller = that._caller; 
+        _next = NULL;
+        return *this;
+    }
+
     /** Attach a static function.
      *
      *  @param function The void static function to attach (default is none).
@@ -73,13 +86,29 @@ public:
      *  FunctionPointers their callbacks are invoked as well.
      *  @Note: All chained callbacks stack up, so hopefully there won't be too
      *  many FunctionPointers in a chain. */
-    void call(ContextType context) {
+    void call(ContextType context) const {
         _caller(this, context);
+    }
 
-        /* Propagate the call to next in the chain. */
-        if (_next) {
-            _next->call(context);
-        }
+    /**
+     * @brief Same as above
+     */
+    void operator()(ContextType context) const {
+        call(context);
+    }
+
+    /** Same as above, workaround for mbed os FunctionPointer implementation. */
+    void call(ContextType context) {
+        ((const FunctionPointerWithContext*)  this)->call(context);
+    }
+
+    typedef void (FunctionPointerWithContext::*bool_type)() const;
+
+    /** 
+     * implementation of safe bool operator
+     */
+    bool toBool() const {
+        return (_function || _memberFunctionAndPointer._object);
     }
 
     /**
@@ -101,9 +130,18 @@ public:
         return (pvoidfcontext_t)_function;
     }
 
+    friend bool operator==(const FunctionPointerWithContext& lhs, const FunctionPointerWithContext& rhs) {
+        return rhs._caller == lhs._caller &&
+               memcmp(
+                   &rhs._memberFunctionAndPointer, 
+                   &lhs._memberFunctionAndPointer, 
+                   sizeof(rhs._memberFunctionAndPointer)
+               ) == 0;
+    }
+
 private:
     template<typename T>
-    static void membercaller(pFunctionPointerWithContext_t self, ContextType context) {
+    static void membercaller(cpFunctionPointerWithContext_t self, ContextType context) {
         if (self->_memberFunctionAndPointer._object) {
             T *o = static_cast<T *>(self->_memberFunctionAndPointer._object);
             void (T::*m)(ContextType);
@@ -112,7 +150,7 @@ private:
         }
     }
 
-    static void functioncaller(pFunctionPointerWithContext_t self, ContextType context) {
+    static void functioncaller(cpFunctionPointerWithContext_t self, ContextType context) {
         if (self->_function) {
             self->_function(context);
         }
@@ -141,10 +179,10 @@ private:
          * object this pointer and pointer to member -
          * _memberFunctionAndPointer._object will be NULL if none attached
          */
-        MemberFunctionAndPtr _memberFunctionAndPointer;
+        mutable MemberFunctionAndPtr _memberFunctionAndPointer;
     };
 
-    void (*_caller)(FunctionPointerWithContext*, ContextType);
+    void (*_caller)(const FunctionPointerWithContext*, ContextType);
 
     pFunctionPointerWithContext_t _next;                /**< Optional link to make a chain out of functionPointers. This
                                                          *   allows chaining function pointers without requiring
@@ -152,4 +190,23 @@ private:
                                                          *   'CallChain' as an alternative. */
 };
 
+/**
+ * @brief Create a new FunctionPointerWithContext which bind an instance and a  
+ * a member function together.
+ * @details This little helper is a just here to eliminate the need to write the
+ * FunctionPointerWithContext type each time you want to create one by kicking 
+ * automatic type deduction of function templates. With this function, it is easy 
+ * to write only one entry point for functions which expect a FunctionPointer 
+ * in parameters.
+ * 
+ * @param object to bound with member function
+ * @param member The member function called
+ * @return a new FunctionPointerWithContext
+ */
+template<typename T, typename ContextType>
+FunctionPointerWithContext<ContextType> makeFunctionPointer(T *object, void (T::*member)(ContextType context)) 
+{
+    return FunctionPointerWithContext<ContextType>(object, member);
+}
+
 #endif // ifndef MBED_FUNCTIONPOINTER_WITH_CONTEXT_H
diff --git a/ble/Gap.h b/ble/Gap.h
index c87c6e3..7eefcd9 100644
--- a/ble/Gap.h
+++ b/ble/Gap.h
@@ -140,10 +140,15 @@ public:
         return (durationInMillis * 1000) / UNIT_1_25_MS;
     }
 
+    typedef FunctionPointerWithContext<TimeoutSource_t> TimeoutEventCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<TimeoutSource_t> TimeoutEventCallbackChain_t;
+
+    typedef FunctionPointerWithContext<const ConnectionCallbackParams_t *> ConnectionEventCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const ConnectionCallbackParams_t *> ConnectionEventCallbackChain_t;
+
+    typedef FunctionPointerWithContext<const DisconnectionCallbackParams_t*> DisconnectionEventCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const DisconnectionCallbackParams_t*> DisconnectionEventCallbackChain_t;    
 
-    typedef void (*TimeoutEventCallback_t)(TimeoutSource_t source);
-    typedef void (*ConnectionEventCallback_t)(const ConnectionCallbackParams_t *params);
-    typedef void (*DisconnectionEventCallback_t)(const DisconnectionCallbackParams_t *params);
     typedef FunctionPointerWithContext<bool> RadioNotificationEventCallback_t;
 
     /*
@@ -892,25 +897,60 @@ public:
     /**
      * Set up a callback for timeout events. Refer to TimeoutSource_t for
      * possible event types.
+     * @note It is possible to unregister callbacks using onTimeout().detach(callback)
      */
-    void onTimeout(TimeoutEventCallback_t callback) {timeoutCallback = callback;}
+    void onTimeout(TimeoutEventCallback_t callback) {
+        timeoutCallbackChain.add(callback);
+    }
+
+    /**
+     * @brief provide access to the callchain of timeout event callbacks
+     * It is possible to register callbacks using onTimeout().add(callback);
+     * It is possible to unregister callbacks using onTimeout().detach(callback) 
+     * @return The timeout event callbacks chain
+     */
+    TimeoutEventCallbackChain_t& onTimeout() {
+        return timeoutCallbackChain;
+    }
 
     /**
      * Append to a chain of callbacks to be invoked upon GAP connection.
+     * @note It is possible to unregister callbacks using onConnection().detach(callback)
      */
     void onConnection(ConnectionEventCallback_t callback) {connectionCallChain.add(callback);}
 
     template<typename T>
     void onConnection(T *tptr, void (T::*mptr)(const ConnectionCallbackParams_t*)) {connectionCallChain.add(tptr, mptr);}
 
+    /**
+     * @brief provide access to the callchain of connection event callbacks
+     * It is possible to register callbacks using onConnection().add(callback);
+     * It is possible to unregister callbacks using onConnection().detach(callback) 
+     * @return The connection event callbacks chain
+     */
+    ConnectionEventCallbackChain_t& onconnection() { 
+        return connectionCallChain;
+    }
+
     /**
      * Append to a chain of callbacks to be invoked upon GAP disconnection.
+     * @note It is possible to unregister callbacks using onDisconnection().detach(callback)
      */
     void onDisconnection(DisconnectionEventCallback_t callback) {disconnectionCallChain.add(callback);}
 
     template<typename T>
     void onDisconnection(T *tptr, void (T::*mptr)(const DisconnectionCallbackParams_t*)) {disconnectionCallChain.add(tptr, mptr);}
 
+    /**
+     * @brief provide access to the callchain of disconnection event callbacks
+     * It is possible to register callbacks using onDisconnection().add(callback);
+     * It is possible to unregister callbacks using onDisconnection().detach(callback) 
+     * @return The disconnection event callbacks chain
+     */
+    DisconnectionEventCallbackChain_t& onDisconnection() {
+        return disconnectionCallChain;
+    }
+
     /**
      * Set the application callback for radio-notification events.
      *
@@ -940,12 +980,10 @@ public:
      */
     void onRadioNotification(void (*callback)(bool param)) {
         radioNotificationCallback.attach(callback);
-        initRadioNotification();
     }
     template <typename T>
     void onRadioNotification(T *tptr, void (T::*mptr)(bool)) {
         radioNotificationCallback.attach(tptr, mptr);
-        initRadioNotification();
     }
 
 protected:
@@ -956,7 +994,7 @@ protected:
         _scanResponse(),
         state(),
         scanningActive(false),
-        timeoutCallback(NULL),
+        timeoutCallbackChain(),
         radioNotificationCallback(),
         onAdvertisementReport(),
         connectionCallChain(),
@@ -1002,8 +1040,8 @@ public:
     }
 
     void processTimeoutEvent(TimeoutSource_t source) {
-        if (timeoutCallback) {
-            timeoutCallback(source);
+        if (timeoutCallbackChain) {
+            timeoutCallbackChain(source);
         }
     }
 
@@ -1017,11 +1055,11 @@ protected:
     bool                             scanningActive;
 
 protected:
-    TimeoutEventCallback_t           timeoutCallback;
-    RadioNotificationEventCallback_t radioNotificationCallback;
-    AdvertisementReportCallback_t    onAdvertisementReport;
-    CallChainOfFunctionPointersWithContext<const ConnectionCallbackParams_t*>    connectionCallChain;
-    CallChainOfFunctionPointersWithContext<const DisconnectionCallbackParams_t*> disconnectionCallChain;
+    TimeoutEventCallbackChain_t       timeoutCallbackChain;
+    RadioNotificationEventCallback_t  radioNotificationCallback;
+    AdvertisementReportCallback_t     onAdvertisementReport;
+    ConnectionEventCallbackChain_t    connectionCallChain;
+    DisconnectionEventCallbackChain_t disconnectionCallChain;
 
 private:
     /* Disallow copy and assignment. */
diff --git a/ble/GattClient.h b/ble/GattClient.h
index b814ede..a4109d3 100644
--- a/ble/GattClient.h
+++ b/ble/GattClient.h
@@ -23,18 +23,23 @@
 
 #include "GattCallbackParamTypes.h"
 
+#include "CallChainOfFunctionPointersWithContext.h"
+
 class GattClient {
 public:
-    typedef void (*ReadCallback_t)(const GattReadCallbackParams *params);
+    typedef FunctionPointerWithContext<const GattReadCallbackParams*> ReadCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const GattReadCallbackParams*> ReadCallbackChain_t;
 
     enum WriteOp_t {
         GATT_OP_WRITE_REQ = 0x01,  /**< Write request. */
         GATT_OP_WRITE_CMD = 0x02,  /**< Write command. */
     };
 
-    typedef void (*WriteCallback_t)(const GattWriteCallbackParams *params);
+    typedef FunctionPointerWithContext<const GattWriteCallbackParams*> WriteCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const GattWriteCallbackParams*> WriteCallbackChain_t;
 
-    typedef void (*HVXCallback_t)(const GattHVXCallbackParams *params);
+    typedef FunctionPointerWithContext<const GattHVXCallbackParams*> HVXCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const GattHVXCallbackParams*> HVXCallbackChain_t;
 
     /*
      * The following functions are meant to be overridden in the platform-specific sub-class.
@@ -241,18 +246,42 @@ public:
     /* Event callback handlers. */
 public:
     /**
-     * Set up a callback for read response events.
+     * Set up a callback for read response events. 
+     * It is possible to remove registered callbacks using 
+     * onDataRead().detach(callbackToRemove)
      */
     void onDataRead(ReadCallback_t callback) {
-        onDataReadCallback = callback;
+        onDataReadCallbackChain.add(callback);
+    }
+
+    /**
+     * @brief provide access to the callchain of read callbacks
+     * It is possible to register callbacks using onDataRead().add(callback);
+     * It is possible to unregister callbacks using onDataRead().detach(callback) 
+     * @return The read callbacks chain
+     */
+    ReadCallbackChain_t& onDataRead() {
+        return onDataReadCallbackChain;
     }
 
     /**
      * Set up a callback for write response events.
+     * It is possible to remove registered callbacks using 
+     * onDataWritten().detach(callbackToRemove).
      * @Note: Write commands (issued using writeWoResponse) don't generate a response.
      */
     void onDataWritten(WriteCallback_t callback) {
-        onDataWriteCallback = callback;
+        onDataWriteCallbackChain.add(callback);
+    }
+
+    /**
+     * @brief provide access to the callchain of data written callbacks
+     * It is possible to register callbacks using onDataWritten().add(callback);
+     * It is possible to unregister callbacks using onDataWritten().detach(callback) 
+     * @return The data written callbacks chain
+     */
+    WriteCallbackChain_t& onDataWritten() { 
+        return onDataWriteCallbackChain;
     }
 
     /**
@@ -279,9 +308,21 @@ public:
      * Set up a callback for when the GATT client receives an update event
      * corresponding to a change in the value of a characteristic on the remote
      * GATT server.
+     * It is possible to remove registered callbacks using onHVX().detach(callbackToRemove).
      */
     void onHVX(HVXCallback_t callback) {
-        onHVXCallback = callback;
+        onHVXCallbackChain.add(callback);
+    }
+
+
+    /**
+     * @brief provide access to the callchain of HVX callbacks
+     * It is possible to register callbacks using onHVX().add(callback);
+     * It is possible to unregister callbacks using onHVX().detach(callback) 
+     * @return The HVX callbacks chain
+     */
+    HVXCallbackChain_t& onHVX() { 
+        return onHVXCallbackChain;
     }
 
 protected:
@@ -292,27 +333,23 @@ protected:
     /* Entry points for the underlying stack to report events back to the user. */
 public:
     void processReadResponse(const GattReadCallbackParams *params) {
-        if (onDataReadCallback) {
-            onDataReadCallback(params);
-        }
+        onDataReadCallbackChain(params);
     }
 
     void processWriteResponse(const GattWriteCallbackParams *params) {
-        if (onDataWriteCallback) {
-            onDataWriteCallback(params);
-        }
+        onDataWriteCallbackChain(params);
     }
 
     void processHVXEvent(const GattHVXCallbackParams *params) {
-        if (onHVXCallback) {
-            onHVXCallback(params);
+        if (onHVXCallbackChain) {
+            onHVXCallbackChain(params);
         }
     }
 
 protected:
-    ReadCallback_t  onDataReadCallback;
-    WriteCallback_t onDataWriteCallback;
-    HVXCallback_t   onHVXCallback;
+    ReadCallbackChain_t  onDataReadCallbackChain;
+    WriteCallbackChain_t onDataWriteCallbackChain;
+    HVXCallbackChain_t   onHVXCallbackChain;
 
 private:
     /* Disallow copy and assignment. */
diff --git a/ble/GattServer.h b/ble/GattServer.h
index 57e8649..6a6324b 100644
--- a/ble/GattServer.h
+++ b/ble/GattServer.h
@@ -26,9 +26,18 @@
 
 class GattServer {
 public:
+
     /* Event callback handlers. */
-    typedef void (*EventCallback_t)(GattAttribute::Handle_t attributeHandle);
-    typedef void (*ServerEventCallback_t)(void);                    /**< Independent of any particular attribute. */
+    typedef FunctionPointerWithContext<unsigned> DataSentCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<unsigned> DataSentCallbackChain_t;
+
+    typedef FunctionPointerWithContext<const GattWriteCallbackParams*> DataWrittenCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const GattWriteCallbackParams*> DataWrittenCallbackChain_t;    
+
+    typedef FunctionPointerWithContext<const GattReadCallbackParams*> DataReadCallback_t;
+    typedef CallChainOfFunctionPointersWithContext<const GattReadCallbackParams *> DataReadCallbackChain_t;
+
+    typedef FunctionPointerWithContext<GattAttribute::Handle_t> EventCallback_t;
 
 protected:
     GattServer() :
@@ -238,12 +247,19 @@ public:
      * @Note: It is also possible to set up a callback into a member function of
      * some object.
      */
-    void onDataSent(void (*callback)(unsigned count)) {dataSentCallChain.add(callback);}
+    void onDataSent(const DataSentCallback_t& callback) {dataSentCallChain.add(callback);}
     template <typename T>
     void onDataSent(T *objPtr, void (T::*memberPtr)(unsigned count)) {
         dataSentCallChain.add(objPtr, memberPtr);
     }
 
+    /**
+     * @brief get the callback chain called when the event DATA_EVENT is triggered. 
+     */
+    DataSentCallbackChain_t& onDataSent() { 
+        return dataSentCallChain;
+    }
+
     /**
      * Set up a callback for when an attribute has its value updated by or at the
      * connected peer. For a peripheral, this callback is triggered when the local
@@ -258,13 +274,25 @@ public:
      *
      * @Note: It is also possible to set up a callback into a member function of
      * some object.
+     * 
+     * @Note It is possible to unregister a callback using onDataWritten().detach(callback)
      */
-    void onDataWritten(void (*callback)(const GattWriteCallbackParams *eventDataP)) {dataWrittenCallChain.add(callback);}
+    void onDataWritten(const DataWrittenCallback_t& callback) {dataWrittenCallChain.add(callback);}
     template <typename T>
     void onDataWritten(T *objPtr, void (T::*memberPtr)(const GattWriteCallbackParams *context)) {
         dataWrittenCallChain.add(objPtr, memberPtr);
     }
 
+    /**
+     * @brief provide access to the callchain of data written event callbacks
+     * It is possible to register callbacks using onDataWritten().add(callback);
+     * It is possible to unregister callbacks using onDataWritten().detach(callback) 
+     * @return The data written event callbacks chain
+     */    
+    DataWrittenCallbackChain_t& onDataWritten() {
+        return dataWrittenCallChain;
+    }
+
     /**
      * Setup a callback to be invoked on the peripheral when an attribute is
      * being read by a remote client.
@@ -281,10 +309,12 @@ public:
      * @Note: It is also possible to set up a callback into a member function of
      * some object.
      *
+     * @Note It is possible to unregister a callback using onDataRead().detach(callback)
+     *
      * @return BLE_ERROR_NOT_IMPLEMENTED if this functionality isn't available;
      *         else BLE_ERROR_NONE.
      */
-    ble_error_t onDataRead(void (*callback)(const GattReadCallbackParams *eventDataP)) {
+    ble_error_t onDataRead(const DataReadCallback_t& callback) {
         if (!isOnDataReadAvailable()) {
             return BLE_ERROR_NOT_IMPLEMENTED;
         }
@@ -302,6 +332,16 @@ public:
         return BLE_ERROR_NONE;
     }
 
+    /**
+     * @brief provide access to the callchain of data read event callbacks
+     * It is possible to register callbacks using onDataRead().add(callback);
+     * It is possible to unregister callbacks using onDataRead().detach(callback) 
+     * @return The data read event callbacks chain
+     */
+    DataReadCallbackChain_t& onDataRead() {
+        return dataReadCallChain;
+    }
+
     /**
      * Set up a callback for when notifications or indications are enabled for a
      * characteristic on the local GATT server.
@@ -323,15 +363,11 @@ public:
     /* Entry points for the underlying stack to report events back to the user. */
 protected:
     void handleDataWrittenEvent(const GattWriteCallbackParams *params) {
-        if (dataWrittenCallChain.hasCallbacksAttached()) {
-            dataWrittenCallChain.call(params);
-        }
+        dataWrittenCallChain.call(params);
     }
 
     void handleDataReadEvent(const GattReadCallbackParams *params) {
-        if (dataReadCallChain.hasCallbacksAttached()) {
-            dataReadCallChain.call(params);
-        }
+        dataReadCallChain.call(params);
     }
 
     void handleEvent(GattServerEvents::gattEvent_e type, GattAttribute::Handle_t attributeHandle) {
@@ -357,9 +393,7 @@ protected:
     }
 
     void handleDataSentEvent(unsigned count) {
-        if (dataSentCallChain.hasCallbacksAttached()) {
-            dataSentCallChain.call(count);
-        }
+        dataSentCallChain.call(count);
     }
 
 protected:
@@ -367,12 +401,12 @@ protected:
     uint8_t characteristicCount;
 
 private:
-    CallChainOfFunctionPointersWithContext<unsigned>                        dataSentCallChain;
-    CallChainOfFunctionPointersWithContext<const GattWriteCallbackParams *> dataWrittenCallChain;
-    CallChainOfFunctionPointersWithContext<const GattReadCallbackParams *>  dataReadCallChain;
-    EventCallback_t                                                         updatesEnabledCallback;
-    EventCallback_t                                                         updatesDisabledCallback;
-    EventCallback_t                                                         confirmationReceivedCallback;
+    DataSentCallbackChain_t    dataSentCallChain;
+    DataWrittenCallbackChain_t dataWrittenCallChain;
+    DataReadCallbackChain_t    dataReadCallChain;
+    EventCallback_t            updatesEnabledCallback;
+    EventCallback_t            updatesDisabledCallback;
+    EventCallback_t            confirmationReceivedCallback;
 
 private:
     /* Disallow copy and assignment. */
diff --git a/ble/SafeBool.h b/ble/SafeBool.h
new file mode 100644
index 0000000..c498508
--- /dev/null
+++ b/ble/SafeBool.h
@@ -0,0 +1,114 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BLE_API_SAFE_BOOL_H_
+#define BLE_API_SAFE_BOOL_H_
+
+//safe bool idiom, see : http://www.artima.com/cppsource/safebool.html
+
+namespace SafeBool_ {
+/**
+ * @brief Base class for all intances of SafeBool, 
+ * This base class reduce instantiation of trueTag function
+ */
+class base {
+  template<typename>
+  friend class SafeBool;
+
+protected:
+    //the bool type is a pointer to method which can be used in boolean context
+  typedef void (base::*BoolType_t)() const;
+
+  // non implemented call, use to disallow conversion between unrelated types 
+  void invalidTag() const;
+
+  // member function which indicate true value
+  void trueTag() const {}
+};
+
+
+}
+
+/**
+ * @brief template class SafeBool use CRTP to made boolean conversion easy and correct.
+ * Derived class should implement the function bool toBool() const to make this work. Inheritance 
+ * should be public.
+ *
+ * @tparam T Type of the derived class
+ * 
+ * \code 
+ * 
+ * class A : public SafeBool<A> { 
+ * public:
+ * 
+ *      // boolean conversion
+ *      bool toBool() { 
+ *      
+ *      }  
+ * };
+ * 
+ * class B : public SafeBool<B> { 
+ * public:
+ * 
+ *      // boolean conversion
+ *      bool toBool() const { 
+ *      
+ *      }  
+ * };
+ * 
+ * A a;
+ * B b;
+ * 
+ * // will compile 
+ * if(a) { 
+ * 
+ * }
+ * 
+ * // compilation error 
+ * if(a == b) { 
+ * 
+ * }
+ * 
+ * 
+ * \endcode
+ */
+template <typename T> 
+class SafeBool : public SafeBool_::base {
+public:
+  /** 
+   * bool operator implementation, derived class has to provide bool toBool() const function.
+   */
+  operator BoolType_t() const {
+    return (static_cast<const T*>(this))->toBool()
+      ? &SafeBool<T>::trueTag : 0;
+  }
+};
+
+//Avoid conversion to bool between different classes
+template <typename T, typename U>
+void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs) {
+    lhs.invalidTag();
+//    return false;
+}
+
+//Avoid conversion to bool between different classes
+template <typename T,typename U>
+void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs) {
+  lhs.invalidTag();
+//  return false;
+}
+
+#endif /* BLE_API_SAFE_BOOL_H_ */
diff --git a/ble/ServiceDiscovery.h b/ble/ServiceDiscovery.h
index 937b4a3..595bc20 100644
--- a/ble/ServiceDiscovery.h
+++ b/ble/ServiceDiscovery.h
@@ -38,7 +38,7 @@ public:
      * framework. The application can safely make a persistent shallow-copy of
      * this object to work with the service beyond the callback.
      */
-    typedef void (*ServiceCallback_t)(const DiscoveredService *);
+    typedef FunctionPointerWithContext<const DiscoveredService *> ServiceCallback_t;
 
     /**
      * Callback type for when a matching characteristic is found during service-
@@ -48,12 +48,12 @@ public:
      * framework. The application can safely make a persistent shallow-copy of
      * this object to work with the characteristic beyond the callback.
      */
-    typedef void (*CharacteristicCallback_t)(const DiscoveredCharacteristic *);
+    typedef FunctionPointerWithContext<const DiscoveredCharacteristic *> CharacteristicCallback_t;
 
     /**
      * Callback type for when serviceDiscovery terminates.
      */
-    typedef void (*TerminationCallback_t)(Gap::Handle_t connectionHandle);
+    typedef FunctionPointerWithContext<Gap::Handle_t> TerminationCallback_t;
 
 public:
     /**
diff --git a/source/DiscoveredCharacteristic.cpp b/source/DiscoveredCharacteristic.cpp
index 5d0133d..91119e0 100644
--- a/source/DiscoveredCharacteristic.cpp
+++ b/source/DiscoveredCharacteristic.cpp
@@ -31,6 +31,52 @@ DiscoveredCharacteristic::read(uint16_t offset) const
     return gattc->read(connHandle, valueHandle, offset);
 }
 
+struct OneShotReadCallback { 
+    static void launch(GattClient* client, Gap::Handle_t connHandle, 
+                       GattAttribute::Handle_t handle, const GattClient::ReadCallback_t& cb) { 
+        OneShotReadCallback* oneShot = new OneShotReadCallback(client, connHandle, handle, cb);
+        oneShot->attach();
+        // delete will be made when this callback is called
+    }
+
+private:
+    OneShotReadCallback(GattClient* client, Gap::Handle_t connHandle, 
+                        GattAttribute::Handle_t handle, const GattClient::ReadCallback_t& cb) : 
+        _client(client),
+        _connHandle(connHandle),
+        _handle(handle), 
+        _callback(cb) { } 
+
+    void attach() { 
+        _client->onDataRead(makeFunctionPointer(this, &OneShotReadCallback::call));
+    }
+
+    void call(const GattReadCallbackParams* params) {
+        // verifiy that it is the right characteristic on the right connection
+        if (params->connHandle == _connHandle && params->handle == _handle) { 
+            _callback(params);
+            _client->onDataRead().detach(makeFunctionPointer(this, &OneShotReadCallback::call));
+            delete this;
+        }
+    }
+
+    GattClient* _client;
+    Gap::Handle_t _connHandle;
+    GattAttribute::Handle_t _handle;
+    GattClient::ReadCallback_t _callback;
+};
+
+ble_error_t DiscoveredCharacteristic::read(uint16_t offset, const GattClient::ReadCallback_t& onRead) const {
+    ble_error_t error = read(offset);
+    if (error) { 
+        return error;
+    }
+
+    OneShotReadCallback::launch(gattc, connHandle, valueHandle, onRead);
+
+    return error;
+}
+
 ble_error_t
 DiscoveredCharacteristic::write(uint16_t length, const uint8_t *value) const
 {
@@ -59,6 +105,52 @@ DiscoveredCharacteristic::writeWoResponse(uint16_t length, const uint8_t *value)
     return gattc->write(GattClient::GATT_OP_WRITE_CMD, connHandle, valueHandle, length, value);
 }
 
+struct OneShotWriteCallback { 
+    static void launch(GattClient* client, Gap::Handle_t connHandle, 
+                       GattAttribute::Handle_t handle, const GattClient::WriteCallback_t& cb) { 
+        OneShotWriteCallback* oneShot = new OneShotWriteCallback(client, connHandle, handle, cb);
+        oneShot->attach();
+        // delete will be made when this callback is called
+    }
+
+private:
+    OneShotWriteCallback(GattClient* client, Gap::Handle_t connHandle, 
+                        GattAttribute::Handle_t handle, const GattClient::WriteCallback_t& cb) : 
+        _client(client),
+        _connHandle(connHandle),
+        _handle(handle), 
+        _callback(cb) { } 
+
+    void attach() { 
+        _client->onDataWritten(makeFunctionPointer(this, &OneShotWriteCallback::call));
+    }
+
+    void call(const GattWriteCallbackParams* params) {
+        // verifiy that it is the right characteristic on the right connection
+        if (params->connHandle == _connHandle && params->handle == _handle) { 
+            _callback(params);
+            _client->onDataWritten().detach(makeFunctionPointer(this, &OneShotWriteCallback::call));
+            delete this;
+        }
+    }
+
+    GattClient* _client;
+    Gap::Handle_t _connHandle;
+    GattAttribute::Handle_t _handle;
+    GattClient::WriteCallback_t _callback;
+};
+
+ble_error_t DiscoveredCharacteristic::write(uint16_t length, const uint8_t *value, const GattClient::WriteCallback_t& onRead) const {
+    ble_error_t error = write(length, value);
+    if (error) { 
+        return error;
+    }
+
+    OneShotWriteCallback::launch(gattc, connHandle, valueHandle, onRead);
+
+    return error;
+}
+
 ble_error_t
 DiscoveredCharacteristic::discoverDescriptors(DescriptorCallback_t callback, const UUID &matchingUUID) const
 {