I was thinking of ways to incentivize myself to keep the weight down and I've played into my vanity a bit so I forbade myself from buying new clothes until I reach the desired weight target. As the easiest way of accepting weight gain is to go out and shop for clothes that fit the new, fatter you.
So I thought of an app or app extension that would block paying with cards in clothing stores or online until a weight goal is reached. Hence, you would have the incentive of your old clothes fitting you badly with the extra weight so socially it would bring a negative emotion of shame to spring you into action towards weight loss. Plus, old clothes tend to rip when you're too fat for them. So this is a "burn the boats" approach to weight loss.
The way I envisioned is that you would type in how many kilograms/pounds you want to have ideally and until you reach that weight your cards would be blocked in clothing stores. In a way that Dating apps have a system for verifying the user's identity, the app could require the user to send a video of them measuring themselves on a scale to unblock their money.
It can be a peer to peer system too where random people check on each other as in the form of alcoholic anonymous sponsors.
On the flip side, the app could be used for people who want to gain muscle mass. For instance, it could be used to block purchasing clothes until your biceps or glutes reach a certain circumference.
If intervening with the process of payment is an impossible task from a coding perspective independently, the project could be launched via a bank or MasterCard or Visa as a community PR action. They might be hard to convince to block their users from spending but an alternative like discounts for gyms memberships (recurring payments) could be made to even out the numbers.
Of course, there's the question of cash payment but I thought that through the Location feature on phones we could battle that too. Let's say that if GPS notes you spent more than two-three minutes in a clothing shop an embarrassing alarm would go off loudly on your phone. Without being able to stop it anyway besides moving far away from the store.
This time activation is necessary because you don't want to activate the alarm every time you pass a clothing store on accident, and it's hard to buy something in less than three minutes.
Of course, some people simply don't care about clothes, so the app could be turned to target a person's favourite hobbies and prevent them from buying board games or whatnot. Or why not even block purchasing at fast-food chains to stop the problem at the root.