oh baffled there are MANY
There are many brands of pod style data collection systems which link to watches, I think nike's is currently the only one that links to an MP3. Google Footpod. Sumpto (sp?) and polar are well respected.
There is also the GPS option (Garmin and a few others)
GPS needs no calibration but does not work well in heavily wooded areas, also if you run in the city with tall buildings, it is less reliable. I have a 305, I have heard good things about the next generation but any GPS needs to be able to recieve a sattelite signal. Elevation is less accurate so hilly runs may measure short. I find typically on an open (suburbs and country) run that the accuracy is within 1-2% - certainly better than my car odometer!
Footpods need calibration and some people find that their stride length changes significantly with pace and have a more difficult time calibrating one than others. But if you run on trails with tree cover they are really the only way to go
I am intrigued because when I googled footpod apparently I can get one to talk to my garmin and have data when I cant get a signal, although I think I would have to choose one or the other for the run.



