well, that's the problem. Getting traction is going to be very difficult with this. You're expecting people to find, or remember this site next time they need to brainstorm something. It's basically a stand-alone "feature".

Marketing is difficult, but more importantly, getting visitors to stick is going to be extremely difficult.

If, on the other hand, you do something bigger, such as create a brainstorming resource site with tips, tricks, and all sorts of useful stuff that will attract visitors - this could be a nice feature to add to that site.