to echo the comment of other satisfied customer , this be what runner have be wait for . a meaningful -lrb- and accurate ! -rrb- speedometer for runner !! I have use this product several time , in a variety of condition and have only receive the weak signal alarm once -lrb- and that be with tree cover and significant terrain -rrb- . while other reviewer have opt to wear the unit on they upper arm , I wear it like a watch and have not have problem . I like the fact that this unit be significantly smaller than the Bodylink unit and be contain in a single unit .  the accuracy be amazing . over a 3.5 mile partially wood trail , the Forerunner differ from a post mileage marker 0.04 mile . on a 25-mile open road bicycle ride , the Forerunner differ from my cyclometer by 0.1 mile -lrb- I assume that the cyclometer need calibration -rrb- .  the ability to load new firmware be a powerful feature of the Forerunner . I upgrade to the latest version upon receive the unit . the process take a few minute and add several new feature . one of the new feature , interval training , be well lay out and easy to customize .  one noticeable downside be no auto-shutoff . while the battery life be advertise at 14 hour , I accidentally leave it on in my briefcase and drain the battery . I hope they fix this in future firmware version .  if you be a casual runner who want to log a couple of hour a week or you be look for a unit to do navigation or geo-caching , look elsewhere . but if you want to keep meticulous track of you mileage and hold to a detailed training plan , the Forerunner be invaluable .