So it's kind of like a crowdfunding site with bitcoin?
At first glance sounds like it, doesn't it? But judging by the chosen example it's a platform to pose challenges to people to do "Jackassy" things.
Like "Run up to a cop and kick him in the nuts!".
Other people that also want to see this can add to the reward for that challenge.
If someone wants the rewards he has to take the challenge and provide proof.
Actually if such a thing was developed it would become a thing really quick. Just look at youtube: People do jackassy stuff for free all the time just for a twisted sense of fame. If you get money involved you can see all kinds of crazy things.
I hope you find a Web-Dev for doing it. I am looking forward to seeing all the crazy stuff that spawns from it.