I just realized something: I want a platform for gauging interest in a project. I don't really want money, I want people to commit to paying $10 for a year's subscription to my idea X (normally costing $200 a year), so I can say "if 100 people find this interesting enough to enter their credit card details, I'm going to go ahead and build it".

Is there currently something like that? A crowdfunding platform will work, I guess, but I want something with more visibility, because I'm bad at discovering and communicating with my target market.

I guess this is a rather hard problem, I might try one of Kickstarter, Indiegogo or a similar platform and see if I'm successful.