diff --git a/source/MicroBit.cpp b/source/MicroBit.cpp
index ebc42b0..2a0acc3 100644
--- a/source/MicroBit.cpp
+++ b/source/MicroBit.cpp
@@ -109,13 +109,11 @@ MicroBit::MicroBit() :
   */
 void MicroBit::init()
 {
-    // Bring up our nested heap allocator.
+    // Bring up the heap allocator, and reclaim as much memory from SoftDevice as possible.
     microbit_heap_init();
 
-    // Bring up fiber scheduler
+    // Bring up fiber scheduler. Wait a little while for state to stabilise.
     scheduler_init(&messageBus);
-    sleep(10);
-
     // Load any stored calibration data from persistent storage.
     MicroBitStorage s = MicroBitStorage();
     MicroBitConfigurationBlock *b = s.getConfigurationBlock();
@@ -129,15 +127,6 @@ void MicroBit::init()
 
     delete b;
 
-	// TODO: YUCK!!! MOVE THESE INTO THE RELEVANT COMPONENTS!!
-	
-    //add the display to the systemComponent array
-    addSystemComponent(&display);
-
-    //add the compass and accelerometer to the idle array
-    addIdleComponent(&accelerometer);
-    addIdleComponent(&compass);
-    addIdleComponent(&messageBus);
 
     // Seed our random number generator
     seedRandom();
@@ -229,6 +218,9 @@ void MicroBit::compassCalibrator(MicroBitEvent)
         int x = accelerometer.getX();
         int y = accelerometer.getY();
 
+	// Wait a little whie for the button state to stabilise (one scheduler tick).
+    sleep(10);
+
         // Deterine the position of the user controlled pixel on the screen.
         if (x < -PIXEL2_THRESHOLD)
             cursor.x = 0;
diff --git a/source/MicroBitAccelerometer.cpp b/source/MicroBitAccelerometer.cpp
index bf2fde9..944e4e4 100644
--- a/source/MicroBitAccelerometer.cpp
+++ b/source/MicroBitAccelerometer.cpp
@@ -157,7 +157,10 @@ MicroBitAccelerometer::MicroBitAccelerometer(uint16_t id, uint16_t address, Micr
 
     // Configure and enable the accelerometer.
     if (this->configure() == MICROBIT_OK)
+	{
+		fiber_add_idle_component(this);
         status |= MICROBIT_COMPONENT_RUNNING;
+	}
 }
 
 /**
diff --git a/source/MicroBitCompass.cpp b/source/MicroBitCompass.cpp
index 49bcf60..c65aa3f 100644
--- a/source/MicroBitCompass.cpp
+++ b/source/MicroBitCompass.cpp
@@ -33,6 +33,8 @@ MicroBitCompass::MicroBitCompass(uint16_t id, uint16_t address, MicroBitI2C& _i2
     // Assume that we have no calibraiton information.
     status &= ~MICROBIT_COMPASS_STATUS_CALIBRATED;
 
+	fiber_add_idle_component(this);
+
     // Indicate that we're up and running.
     status |= MICROBIT_COMPONENT_RUNNING;
 }
diff --git a/source/MicroBitDisplay.cpp b/source/MicroBitDisplay.cpp
index 707f85d..cc8cae0 100644
--- a/source/MicroBitDisplay.cpp
+++ b/source/MicroBitDisplay.cpp
@@ -49,7 +49,9 @@ MicroBitDisplay::MicroBitDisplay(uint16_t id, uint8_t x, uint8_t y) :
 
     if (!this->defaultDisplay)
         this->defaultDisplay = this;
-    
+
+	fiber_add_system_component(this);
+
     status |= MICROBIT_COMPONENT_RUNNING;
 }
 
diff --git a/source/MicroBitEvent.cpp b/source/MicroBitEvent.cpp
index b6294a9..d9c0d04 100644
--- a/source/MicroBitEvent.cpp
+++ b/source/MicroBitEvent.cpp
@@ -42,11 +42,13 @@ MicroBitEvent::MicroBitEvent()
   */
 void MicroBitEvent::fire(MicroBitEventLaunchMode mode)
 {
-    if (mode == CREATE_AND_QUEUE)
-        MicroBitMessageBus::defaultMessageBus->send(*this);
-
-    else if (mode == CREATE_AND_FIRE)
-        MicroBitMessageBus::defaultMessageBus->process(*this);
+	if(MicroBitMessageBus::defaultMessageBus)
+	{
+		if (mode == CREATE_AND_QUEUE)
+			MicroBitMessageBus::defaultMessageBus->send(*this);
+		else if (mode == CREATE_AND_FIRE)
+			MicroBitMessageBus::defaultMessageBus->process(*this);
+	}
 }
 
 /**
diff --git a/source/MicroBitFiber.cpp b/source/MicroBitFiber.cpp
index 0aef7a0..1f4387f 100644
--- a/source/MicroBitFiber.cpp
+++ b/source/MicroBitFiber.cpp
@@ -884,7 +884,7 @@ void idle()
     
     // If the above did create any useful work, enter power efficient sleep.
     if(scheduler_runqueue_empty())
-    	__WFI();
+    	__WFE();
 }
 /**
   * IDLE task.
diff --git a/source/MicroBitMessageBus.cpp b/source/MicroBitMessageBus.cpp
index 6492a13..86a3bdc 100644
--- a/source/MicroBitMessageBus.cpp
+++ b/source/MicroBitMessageBus.cpp
@@ -19,6 +19,8 @@ MicroBitMessageBus::MicroBitMessageBus()
     this->evt_queue_tail = NULL;
     this->queueLength = 0;
 
+	fiber_add_idle_component(this);
+
 	if(MicroBitMessageBus::defaultMessageBus == NULL)
 		MicroBitMessageBus::defaultMessageBus = this;
 }