If the Terminator could headbang, it would probably be a direct descendent of the Guitar Heronoid, a robot created for the purpose of, well, SHREDDING ON GUITAR HERO. It uses image processing code to "follow" the path of the little nodes on-screen and responds accordingly. Check it out in action.
Thinking of your own robotics projects? Check out our over a hundred books on the subject.
Oh, by the way, we are still having the Guitar Hero 2 tournament on Monday. It starts at 12:00 PM. Even if you aren't registered, we have door prizes for just showing up. Yes, that ties in with my new library theme: "Our giveaways. Let me show you them."