Control an arduino pro mini tank via nRF51822-04AT UART LE Bluetooth 4 module and MX1508 DC motor driver. Android App Code is very hacky kick ass app based on my UART Smartwatch App. A big buggy, but ok.
Tank control: forward, backward, left, right, some Buttons to display a Emoji on ST7735 TFT Display.
You can get a signed APK from here