The RasPiComm is an easy way to add extra functionality to the Raspberry Pi, docking with the Pi's header unit to provide more ports and -- hooray! -- a backup battery so the thing can remember what time it is when powered down.
The board's being sold for the equivalent of 36 euros from German site Raspberry Pi Projeckte, offering serial RS-232 and RS-485 compatibility for easier PC and robotics connectivity, plus a five-way joystick connector for unlocking the world of super-easy control input.
The creator's also released the control software for even easier fiddling. You'll have a rudimentary toast buttering machine fabricated within hours.