Being equipped with a Garmin Forerunner 210 watch, I bought this accelerometer in order to know my current speed. This works fine, there is even the possibility to calibrate. I also enjoyed a 10km race specifically for that. My watch showed me too 100m (1% error). The ANT + wireless connection with the watch is done without difficulties. By cons, my speed curve is still sawtooth when I upload my data to Garmin connect, just a little less pronounced than without. Basically, I would say that I can view my current speed in the race (or stage) to + or less 0.5km / h near whereas before I did not have that information during the race. Obviously, on average it's okay after, but it was already on the watch via GPS. I gain precision on sessions like VMA 30/30, it is obviously short distances driven on beaches in 30 seconds, and there, with the GPS, it's limit. For people who run on carpet, GPS is of no use, the accelerometer will give you the information display of the carpet gives you surely also.
