The Antbot
This is the original Android robot platform from 2010, now fully open sourced. Contact me for electronics schematics. Will work with a Picaxe, Arduino, Propeller or MSP430 microcontroller. The motors are a Tamiya 70168 twin gearbox kit.
You can make a battery out of two laptop battery cells, and it'll fit right past the motor. Four AA cells will also fit.
Videos here: https://www.youtube.com/user/Spiritplumber
Android app here: https://play.google.com/store/apps/details?id=re.anywhere.client
Video of this particular Antbot here: https://www.youtube.com/watch?v=hqrzer7aG-c&feature=youtu.be (Credit to Ahmet Oguz)
Be sure to check out my other work at https://www.robots-everywhere.com/