Nice article at the NY Times about fitness gadgetry: By Data Obsessed.
I've got a Polar heart rate monitor and a little Cateye bike computer that does cadence. I do have my eye on the new Polar CS200cad computer that rolls both devices into one. I've also thought it would be nice to have one of the Garmin Forerunners (101 or 102--the 301 is simply too much) for running purposes, although it is hardly needed for running on the lakefront.
A PowerTap would be sweet, but I'm hardly the sort of cyclist who'd really benefit from one since I only ride once or twice a week. Oh, and it costs nearly twice what I paid for my bike.
