Looks like fun, perhaps a little frustrating to control -
Motors inside the ball work against a counterweight to allow it to move without external wheels. I believe certain pitches and sequences control how it moves. It can also play music itself–a piezo actuator uses the entire outer shell as a speaker to play back manipulated portions of what it hears. From a Robotics and Art conference that was taking place near RoboCup 06.
Related: The Zygote interactive ball -Link
From The Maker Store: Blubber Bot Robotic Inflatable -Link