I picked up an ADK board from Google I/O and did this with it the other night to demo it at the Androids in Auckland meetup (shameless plug).

If anyone is interested to see the maze in person, I'll be demoing it at Tangleball's open day on Monday at some time between 1-3pm (second shameless plug, thanks to Abhishek for inviting me along!).

Anyone else out there got one?  Or hacked together a standard Arduino board to work with the accessories API?  I'd be interested in hearing anything that's out there.  The ADK is a sweet platform.