These "Mini-Robots" developed at Sandia National Labs are powered by three watch batteries, use a tank-like track for locomotion, and can be built to include microphones, cameras, or heat and chemical sensors. The bodies are chassis are built from a rapid-prototyping rig. They are available in Regular and Cool Ranch.
BotJunkie has a video of the little stinkahs in action.
Sandia Mini-Robot Turns On Dime, Parks On Nickel [BotJunkie.com]