Anybody know of a service where multiple people can deposit money and I can optionally accept or decline all of it at some later date? Hmm, that makes no sense. Here's what I want to do:

1) I've developed a product that I've sold to many users
2) I'm considering an update to the product. I'm wondering if there is enough demand to make it worthwhile.
3) I'm going to tell my users "if you want an update, make a donation to service X. I'll do an update if I get Y dollars in donation."
4) If I don't get Y dollars, all the money is returned. (or credit cards are never charged). If I do get Y dollars, I can accept the money and then do the update.

Is there a service that does that?