My wife and I just launched this app because we had so much fun with a fitness challenge we did we some friends recently where everyone put in $100 and defined their goals, then only the people who met their goals split the pot. It made us realize there's really no better motivator than money.
It's better on mobile screens right now as we just designed for mobile screens for now. And we did manage to put it up on both app stores - it's low in the ranks but you should be able to search it by "Goalie challenges".
We built it using the leanest tech stack - Ruby on Rails, server-side HTML (no JS), tailwindcss, then packaging it for iOS and Android using pwabuilder!
Essentially, when you externalize a reward, people are less likely to want to continue doing the thing. I suspect this is similar, but it’s externalizing the loss. If you’re not already invested in succeeding, this isn’t going to change that.