Our very first moving cellbot running on Android is the Tankbot. It is based on a simple Tamiya tank tread base, with two continuous rotation servos to drive it. An Arduino board acts as the bridge between an HTC Dream/G1 phone and the motors. The communication is done over serial commands out of the USB port on the bottom of the phone.
This video shows an early working prototype that accepts very simple commands via telnet from a PC. We’ve also tested connecting in via telnet from another Android phone and that works too.
You can get the Python and Arduino code for this on our Google Code project page. More pictures of the project are in this slide show and we’ll have additional instructions coming.