The PiBot is a small robot powered by a Raspberry Pi controlled by an android application. The android application communicated with the Raspberry Pi via a wifi network which in turn controls the motors to move the robot around. This is template implemented to show how an android app could be used to communicate with a Raspberry Pi. You could add more functionalities like sensors and make the bot more purposeful. Creativity is your limit...or sometimes 512 MB RAM.
I was responsible for the android application which acted as the client and the raspberry pi java script which acted as the server. The robot and the android application communicated using simple HTTP + sockets via WiFi hotspot. The project has been made open source under Apache License Version 2.0 and is available in GitHub.