The Wheelphone robot can become your best friend thanks to this application that transforms the robot in an interactive pet. Beware...the Wheelphone will not stop following you.
A behavior module allows showing expressions and behaving accordingly. Additionally has a face-tracking and text-to-speech modules to be able to interact with the environment.
More information about this application, how to use it and the source code are available in the Wheelphone wiki http://www.gctronic.com/doc/index.php/Android_software#Wheelphone_Pet.