[i]something different, creative, not the regular theremin[/i]
How about a maze-solving theremin-guided singing robotic turtle?
http://en.wikipedia.org/wiki/Turtle_(robot)
http://en.wikipedia.org/wiki/Maze#Pledge_algorithm
Attach a pitch only theremin to the top of a turtle, create a circuit that resonates when the theremin plays a specified pitch, flagging a collision event to the turtle which is running the Pledge algorithm. Line the walls of a maze with foil and listen to it warble it's way out.
(If you do this you HAVE to post it on youTube, ok?)
PS Light [i]is[/i] a form of electromagnetic radiation!
However, as I learned at college, you get marks deducted for being a smart-arse. Like the time I discovered it was quite legal to declare "FORTRAN" in a COBOL program, so I effectively coded my assignment in FORTRAN although, strictly, it was still a COBOL program. It compiled and worked perfectly, which is more than can be said for the other students' submissions, and got the lowest mark of the class. :-(