I just completed my 5th steps challenge on Workit (only available on iOS, sorry).
This challenge was 10k steps every day for two weeks. Of course, these were the coldest two weeks of the year, so many of those steps were indoors.
The buy-in/stake was 25k sats and the payout was 28,608, which was a little less than I expected. I don't think the winners of the bonus rewards have been announced yet, so there may still be another 40k coming my way (but, probably not).
So far, I've netted over 50k on these challenges. What a great way to stay healthy, while stacking sats.