Cool, I had an idea about trying something like that once, but using a
turntable instead of a pizza box...
Hmmmm, a optical cartridge.... How many wires do those sensors in optical mice need? you get 4 on a turntable but the grounding might muck it up.
Probably much lighter on the CPU then analysing one of those timecode records, at least.
BTW; That company that did GuitarHero trademarked "TurntableHero" a while ago, or so I read. That might result in interesting controllers. My Beatmania toy turntables only sense movement and direction, not speed so I could use some improvment there.
Kas.