Does anyone use a computer while riding on a trainer to track indoor mileage? How do you do it? I don't want wires running all the way down my frame from the handle bars to the rear wheel, and I thought the solution was a wireless computer with the magnet on the rear wheel, so I bought an inexpensive wireless computer and hooked it up, only to find that the distance from the rear wheel to the front of the bike was too far for signal to travel. Any wireless units that do work on the rear wheel?