Without planning to do so, I presently have three active activity trackers. Two kindof agree, and one reports wildly lower counts. The only category all three report is steps. My ancient Fitbit One and my iPhone report similar step-counts, but, providing I remember to carry it all the time, the iPhone will have a higher step-count than the Fitbit (attached to my underwear). The Nokia Steel HR always reports a much lower value each day, like around 20% lower than the other two.
I noticed this variation, and began to watch more closely. I’m pretty sure that if you consider footfalls “steps,” which I think the devices do, the most accurate of the three trackers is the iPhone, the one that consistently gives the highest count.
Your counts may vary.
I can wear the Nokia in the shower, and it gives me a chunk of steps for that (which does’t “fix” the discrepancy, BTW), and sometimes enquires if that time was an “activity.” It’s those rapid little steps to soap, rotate, and bend to get clean?