I would say alittle above reg fee. I would suggest creating a small site and include a few ban checkers. If memory services me right, there are some programs/scripts that can check and see if someone has banned you on IM.
dunno. There's no way to check banned you or not, you can be banned from thousands of places. I cannot think of any use. I doubt it could count all my bans
As for development ideas, I can't think of any. Swimjenni had an idea, but I've never heard of such programs, so I couldn't recommend that one way or another.