The RaspberryPi is a wonderful small computer. The Arduino is unsurpassed in interfacing with all kinds of hardware. Combining the power of these platforms is certainly not new...
With YARA-Board I have tried to solve a number of problems with one board.
1 - add an Arduino Leonardo to the Raspi to create a YUN-like system
2 - add ATX-like powerswitch top thee Raspi
3 - add support for cheap Rtc module
4 - add support for cheap display modules
5 - add Raspi breakout headers
6 - add IR receiver
To implement the powerswitch I used an attiny45 that also could be controlled from the IR receiver.
The board is ready and I'm currently working on additional software such as arduino ANSI display emulator, YUN-bridge port for the Raspi or other equivalent lib.