The Sphero is robotic remote-controlled ball that can be directed with an iPhone, iPad, iPod touch, or Android device. Controlling Sphero from your mobile device is accomplished in a variety of ways including tilting and gesturing on your device.
The Sphero comes with apps for you device that allow you to play with it in different ways. They call this "Mixed-Reality Game Play" in which real objects and virtual elements are both used for a game. The possibilities seem endless. I love the idea of setting up obstacle courses for it. You could improvise a most unusual indoor miniature golf course with little more than the things already in your living room. There is also the intriguing possibility of fooling your friends and annoying your cat. The Sphero can also be programmed to perform a recorded sequence of actions so that it can then run semi-autonomously.
Here is where you can read a whole lot more about the Sphero Robotic Ball.