Hey Folks - maker of Liftz here (launched v1.0 here a while back: adaptive workouts based on daily readiness).
Just shipped the feature I'm most excited about: Hunt. It GPS-tracks your walks, awards points per km, and rolls everything into a monthly leaderboard. Top finishers win real Amazon coupon rewards after a manual anti-abuse review no automated payouts yet, still small enough that I review winners myself.
The August round opens Aug 1, and I'm opening the first two monthly rounds to everyone free, no premium required, to see if a competitive/rewards layer on top of walking actually drives retention or if it just ends up feeling gimmicky.