I've recently added support for serial comms via USB/OTG to Arduino boards, so if anyone has an Arduino board lying
around and would like to have a go then let me know (
da...@androidscript.org) and I'll send you the appropriate alpha version.
This will let you use an Arduino board as a USB IO device for your Android Phone... Now you can control stuff in the real world!
I've only tested it on an Arduino Uno so far, but it should work for any Arduino board in theory.
I've got a sample App and Arduino sketch to get you started too :)