You may have seen the press release today regarding
Oregon-based Tech Company, APlus Mobile, Announces Launch of the MotherBone™PiOne™ Via Kickstarter
MotherBone™PiOne™ is an all-in-one 3.5" peripheral voltage isolating motherboard for the BeagleBone Black and Raspberry Pi Model B computers that expands and isolates all of the unused default pins of the BeagleBone Black internal resources. In addition, MotherBone™PiOne™ creates two different on-board communication links between Raspberry Pi and BeagleBone Black for advanced control functions allowing both modules to run individually or simultaneously in the real world.
You can find the Kickstarter campaign here: http://kck.st/1gPeOHC
Datasheet and System Reference Manual can be found here: http://aplusmobile.com/MotherBone.html