Craptastic Faceplates
A while back, I had an idea about how to keep thieves from stealing my CD player: Craptastic Faceplates (R)(TM).
The Craptastic Faceplate would look just like the front of an old beat-up 8-track player, a Radio Shack AM/FM-only receiver, or best of all, a Sparkomatic tape deck with one knob missing. They would be completely non-functional, but would fit the faceplate slots for most high-end car stereos. That way you could easily swap out the real faceplate with the decoy when you had to park your car in some unsavory neighborhood [like where Robert lives].