1. The irreversible, binding contract element needs to be exceedingly clear and simple to understand as soon as someone opens the app for the first time (“you will not be able to contact us to reverse the contract, so choose your terms carefully”). Additionally, give users the reason why the contract is irreversible up front so that they understand the app’s foundations. I would want the contract to be irreversible, that’s a feature not a bug, but users should know that. Users who aren’t comfortable with that should ideally be offered a weak alternative as long as that doesn’t muddy the service. Otherwise, turn them away.
Even the button that users press to agree to a contract should be called the “No Way Out” button or something like that. However, great care should be taken to ensure that users who behave well don’t get punished (e.g. agreeing to pay $X if you don’t lose weight, and you lose weight but there’s a bug with reporting that, or the app doesn’t ping you enough to warn you to check in, or you don’t understand the consequences of not checking in, or there wasn’t enough granularity with the terms of checking in). Users who don’t trust the app as an automatic executor of contractual punishments should be able to designate a third party arbitrator, like a friend or parent, but that shouldn’t be the default option. Maybe the user’s friends will be lenient, but let them find that out.
2. They have both a “charity” and “anti-charity” option, which is fine. However, the structure of the “charity” option is problematic. It is not clear to users picking that option that their funds may go to a charity they actually dislike, making it more of an Anti-Charity. Additionally, for both the charity and anti-charity options, they should let the user choose their level of granularity. If a user wants to designate specific organizations, let them make that trade off. Maybe someone is willing to make a particular political party their anti-charity, but never in a million lifetimes the Coalition for Coal (made up). “Charity” and “Anti-Charity” are vague. There’s a fine line between motivating your users and provoking unmitigated rage in this space. If that’s hard with the “charity” and “anti-charity” categories, maybe they should be scrapped entirely.
3. It seems like they have UI, usability, and bug issues.
Again, I think that the concept behind their app is great, and they have a lot of potential, but there’s an opportunity for you to do everything they do but better.