Bitty Blue provides a collection of fun things to do with a BBC micro:bit (or compatible device) and Bluetooth. Play with 3D "PolySquiggles", use your micro:bit as a compass, have fun with the micro:bit's buttons, design patterns and send them or text to the micro:bit LED display. You can also monitor the temperature and get alerted if it gets too cold or too hot or just send messages from your micro:bit to your phone to be displayed. Lots of fun and educational too!
This application is available for iOS and Android smartphones.
Note that with the standard bitty data logger installed on your micro:bit, you will need to calibrate the internal ditigal compass whenever your micro:bit starts. Follow the on-display instructions.