I want a cheap computer (preferably with cadence) for the bike on the trainer. Need something that works off rear wheel. Nashbar has a Blackburn Delphi 3.0 that I'm ordering but I don't know if the wiring is long enough for me to mount on the rear wheel. Anybody got any ideas?

I don't know if any computers have long enough wires to reach the rear wheel, or if the wireless ones have enough range to work with the sensor on the rear wheel, but if you needed to it would be a relatively simple matter to take a wired computer and cut the wire and solder in a longer length that's as long as you need.

It's just two wires, nothing fancy. It generally goes to a reed switch in the sensor, so you don't even need special wire (such as coax) -- anything will do.

Sheldon Brown does seem to suggest that there are computers meant for installation on the rear wheel.

I should also mention that this question has come up before and gotten good answers.