TQi and the iPod interface is an awesome idea. love it.

I found that many racers like to use a personal lap counter to keep track of their times.

I was thinking about it, and it is not that difficult in hardware to add this to the TQi:
- IV emitter in the border of the track
- IV receiver in the side of the model
- reading just like the RPM counter, only much much slower
- - every time the receiver gets a IV exposure, 1 lap count, 1 rev

The software interface, I have no idea of how much work will be necessary, but in terms of hardware... you already have the difficult part, the counter that is the RPM.
the rest is just the emitter and receiver, basic stuff.