to wind30:
dammit the quote button on this forum doesn't seem to be working today.
I use the S625X which has the same footpod as the one that comes with the RS200sd. The footpod looks big but once you have it on your shoe you can't tell its there. So its comfortable as wearing nothing.
Its accurate as well. The first time I calibrated, it was + - 3-5% of the actual distance (ran with GPS to compare). Tried to check again this year since my speed has improved, and it was still within 3% of the GPS. Before you think about buying one with GPS measurement device, check out the place that you run first. GPS are notoriously dodgy when there are trees or if you run in the city with a lot of tall buildings. (Maybe the new GArmin ForeRUnner s have a better GPS reception though, but never tested)
If you're crazy about it. Polar just released the RS400 and RS800. I think they should be beyond the budget of almost everyone except the pros.