Meet the Adafruit Feather Bluefruit: an Arduino-compatible development board with Bluetooth and built-in USB. As you can see in the above GIF, you can communicate with this board form your iOS or Android device. The Feather 32u4 has a ATmega32u4 microcontroller. The chip has 32k of flash, and 2k of RAM. The board measures 2.0″ x 0.9″ x 0.28″. You can find out more about it here.