I finally got my first prototype which I'll show at the Embedded World
in a week.
It's a voltage conversion base board which enables you to connect a 5V
Arduino shield to a Beagle Bone Black.
What you can see here is a Grove shield connected to it. Now you can
connect many different sensors/actors to the BBB.
Left from the BBB are even more pins on Grove connectors (with 5V
conversion) and lots of jumpers to jumper what goes where.
 http://www.reliableembeddedsystems.com/images/Hw4SWppl.jpg  http://www.seeedstudio.com/wiki/Grove_System