A Stanford inquiry into the accuracy of seven wristband activity monitors showed that six out of seven devices measured heart rate within 5 percent. None, however, measured energy expenditure well…
…“People are basing life decisions on the data provided by these devices,” said Euan Ashley, DPhil, FRCP, professor of cardiovascular medicine, of genetics and of biomedical data science at Stanford. But consumer devices aren’t held to the same standards as medical-grade devices, and it’s hard for doctors to know what to make of heart-rate data and other data from a patient’s wearable device, he said… More at Stanford Medicine.
Seems that we have a long way to go in terms of how these devices can measure individuals.
I know a few people who wear an Apple Watch and the calories burned is markedly different between each person. It should of course be this way, but at times the differences are so different that they make little sense. At least the Apple Watch is the best for heart rate sensing I guess.