Maii is a small creature that brightens on the days you do something for yourself: stand on one leg, count reps, breathe, photograph a meal.
Start with the one-leg balance test at maii.health/try. No account needed: prop your phone up and its camera times you, eyes open or shut. The picture never leaves your phone.
Then dare someone. Send the link: they see your time, try to beat it, and every try lands on that link's board.
It works in the browser, no app to install.