Before I moved to the Idea of incorporating an AT Mega 328 on the board and basicly providing an integrated
Arduino system I was looking at a prototype pad board bare and uncommited except for the 2 A 5V DCDC
converted to "Juice Up" the Pi.
We've subsequently tidied up the design and can make a batch of PCBs available if people express an interest.
The original Article has more information.
http://shropshirelug.wordpress.com/2011/12/10/mopi-a-prototype-board-for-raspberrypi/
John