Subject: RE: Choosing a new GPS deviceI don't have any of these...yet. The cadence sensor does 2 things for you. It provides cadence, indoors or out, and serves as a sensor for speed when indoors or otherwise out of GPS range. So yes, works on the trainer! And tunnels and whatever. I'm leaning towards the 310xt myself. Especially since I have a buddy working at Garmin. His discount on the 305 is laughable but HUGE on the 310. They are allowed 10 units a year at their discount for themselves/friends/family. Glad I asked him about it, and I think I'll pick one up soon. FWIW, I also like the look of the Timex unit, but Garmins are tried and true. (And I don't have any connections at Timex.... ) -eric |