Thank you all for your input.

I realize that this would be pretty easy to do with a computer and that may be the way to go. It would be cool, however, to have a small box that you could plug a TV or monitor into one side and and anolog audio signal in the other to get cool visuals.

Hmmm, If I were to design one, it would have to have decent graphics capabiliies, multiple output types, and possibly an interface with a computer to update/add visuals.

Kind of a cool concept. I will probably never get to it, though :P