Added documentation for Bluetooth accelerometer service

docs/reference/bluetooth/start-accelerometer-service.md

@@ -0,0 +1,38 @@
+# Bluetooth Accelerometer Service 
+
+![](/static/bluetooth/Bluetooth_SIG.png)
+
+The Bluetooth accelerometer service allows another device such as a smartphone to wirelessly receive data from the micro:bit's accelerometer. An accelerometer detects motion. More precisely, it measures acceleration in one or more of three directions which we call X, Y and Z. 
+
+Using the Bluetooth accelerometer service you could, for example, create a smartphone application which makes a loud noise whenever your micro:bit (or the important thing you've attached it to) is moved. Or you could use your micro:bit to control the movement of a cartoon character in a game on your smartphone just by tilting the micro:bit in the direction you want the character to move in.     
+
+No additional code is needed on the micro:bit to use the Bluetooth accelerometer service from another device.
+
+~~~~sig
+bluetooth.startAccelerometerService();
+~~~~
+
+### Example: Starting the Bluetooth accelerometer service
+
+The following code shows the Bluetooth accelerometer service being started:
+
+~~~~blocks
+bluetooth.startAccelerometerService();
+~~~~
+
+### Video - Accelerometer service demo - Starts at 0:18
+
+[![micro:bit Bluetooth demo video](/static/bluetooth/microbit_accelerometer.png)](
+    http://www.youtube.com/watch?v=aep_GVowKfs "Click to launch YouTube video"
+    )
+
+### Advanced
+ 
+For more advanced information on the micro:bit Bluetooth accelerometer service including information on using a smartphone, see the [Lancaster University micro:bit runtime technical documentation](http://lancaster-university.github.io/microbit-docs/ble/accelerometer-service/)
+
+### See also
+
+[Bluetooth SIG](https://www.bluetooth.com)
+
+[Bluetooth on micro:bit resources](http://bluetooth-mdw.blogspot.co.uk/p/bbc-microbit.html)
+