Thanks for the replies. So if using the KPH readout I'd want to use a wheel circumference of 1667 mm....right ?

I wasn't trying to determine distance, just cadence. I already use a HRM and just wanted to be able to be consistent with my cadence.

I didn't consider putting the sensor on the crank, which, as I now think about it, really is the easiest way to get where I wanted to go...now if I could just figure an easy (cheap) way to monitor power input....