They just said that they are "looking into lap counters now." I'm going to wait another month or two on finding an inexpensive RF one (I'd prefer one that takes the regular 27MHz crystals just like the cars) before working on building one. I've got an electromagnetic induction-based "ping" transponder idea I want to get working, but it's been ages since I've built any circuits, so I've got some work to do on theory.