I built a web app that lets you share your goals publicly, together with a pledged amount. If you achieve your goal, great! Else, you pay the pledged amount as a fine to me. Sounds goofy, but I hope it provides the extra reason for you to keep going when the going gets tough!
All the money goes directly into my pocket, with none of it being allocated for positive purposes, such as charitable donations. So, as a user, you should be motivated to persist in pursuing your goal.
Could be interesting to allocate the funds to something related to the goal, either for or against it, to make reaching the goal that much more motivating
Not if it goes against the user, f.x. if the user wanted to start helping a nature conservancy but don't, then make a payment to a motorsports driver or logging company