The brains board that meArm sells for controlling the thing is pretty pricey, so we thought we would just design our own. The setup is actually two boards. The larger board is processor board, and the smaller one is the joystick board.
The processor board will attach to the meArm base, and uses a cheap Arduino Pro Mini clone that you can get off ebay for around $3, to controll the servos. The processor board also has a few extra IO pins that could be used for extra servos (I’m thinking of a base with two continuous rotation servos driving wheels) or other sensors, and a IR receiver so that it can be controlled with a IR remote such as your TV remote, or the LEGO power function remote.
The small board is the joystick board. It accommodates 2 analog joysticks and 3 push buttons. The joystick board is connected to the processor board with a ribbon cable.