BrickPi is a mash-up of the Raspberry Pi microcomputer, co-opted to act as the brains of the robot, plus LEGO Mindstorms sensors, bricks and motors for crafting its working parts.
Firmware is written in Arduino, making it open and hackable (the BrickPi makers have put their hardware designs and software source code online for download on Github).
The BrickPi extends the Raspberry Pi with a board that snaps in place over the Pi to connect it to the various LEGO sensors (such as touch sensors, colour sensors and gyroscope). This is then contained within a plastic case that is compatible with LEGO bricks so it can act as the base for building out the robot. An on board battery connector allows the robot to be untethered from a power socket so it can go roving.