I personally liked the PAI approach from the Mi Band where you get points for various activities, depending on the heart rate during the activity. You loose the points after a week - motivating you to continue and also the points are harder to get the better you get at the activity, because of the lower heart rate. I know, it’s all smoke and mirrors, but I I liked that approach for the same reasons you mentioned.
Not to forget that around 70% of the revenues cone from a single, non-disclosed, customer. My wild guess: it’s Google…
EDIT: And they just significantly reduced their expenditures for Software Development…