A good friend of mine, Blake Foster, along with a couple of other students designed this as part of their graduate research. They even supply a parts list and the software they developed.
UMass Graphics & Vision Research: Realtime Tracking With a Pan-Tilt Camera
Here's a YouTube Video
The human eye is amazingly adept at tracking moving objects. The process is so natural to humans that it happens without any conscious effort. While this remarkable ability depends in part on the human brain's immense processing power, the fast response of the extraocular muscles and the eyeball's light weight are also vital. Even a small point and shoot camera mounted on a servo is typically too heavy and slow to move with the agility of the human eye. How, then, can we give a computer the ability to track movement quickly and responsively?
UMass Graphics & Vision Research: Realtime Tracking With a Pan-Tilt Camera
Here's a YouTube Video