[necovek]

You are not making the distinction between objective value of fitness trackers (they can measure speed, pace, heart rate, SpO2...), which allows for actionable recourse (I am getting worse/stagnating/improving in this particular area), and sociological/psychological value they are providing.

I think it'd be hard to say measuring something in order to improve on it is useless: and most of the smart devices allow one to extract exactly that value.

Now, I wouldn't be the one to discredit social and psychological value for any smart devices, because they can be very real too, but it's definitely obvious that we should look for alternative solutions to those problems at the same time.