For another device like a smartphone to use any of the Bluetooth "services" which the @boardname@ has, it must first be [paired with the @boardname@](/reference/bluetooth/bluetooth-pairing). Once paired, the other device may connect to the @boardname@ and exchange data relating to many of the @boardname@'s features.
The Bluetooth accelerometer service allows another device such as a smartphone to wirelessly receive data from the @boardname@'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 @boardname@ (or the important thing you've attached it to) is moved. Or you could use your @boardname@ to control the movement of a cartoon character in a game on your smartphone just by tilting the @boardname@ in the direction you want the character to move in.
For more advanced information on the @boardname@ Bluetooth accelerometer service including information on using a smartphone, see the [Lancaster University @boardname@ runtime technical documentation](http://lancaster-university.github.io/microbit-docs/ble/accelerometer-service/)
