Kirk McElhearn puts a Fitbit One and his Apple Watch through their paces, to get a sense of the accuracy of the Apple Watch as a fitness tracker.

Lots to read here, but from his conclusion:

I’ve said before that fitness trackers are more about motivation than accuracy. If they get you to be more active, by prodding you to reach new goals, then they are successful. They should give you reliable data about your activity, though, and not be far off the mark. (I consider that the 5% difference in step count is acceptable.) But they shouldn’t lead you to wonder whether your activity is counted correctly, as the Apple Watch does. Either the Apple Watch is severely flawed in its fitness tracking capabilities, or I received a dud (I’m going to call Apple later to try and find out). I’m curious as to whether other readers have compared the Apple Watch with other fitness trackers, or whether anyone has similar data, reported by the Apple Watch, which just seems wrong.

I think accuracy is incredibly important if you use your Apple Watch to manage your personal health. The difference between a long run at 150 BPM and 145 BPM is not a big deal, but a run at 160 BPM when you think you are at 140 BPM can be life threatening, more so the older you get.

Obviously, as Kirk points out, accuracy in step counting is less critical, but it is important. If one device can get it right, then Apple should be able to get it right.

Clearly, this is Apple’s first kick at the can here, their first shipping medical sensor and their first activity tracking device. I have no doubt that, just like Apple Maps, Apple’s medical and fitness efforts will continue to evolve, continue to get more accurate over time.