This is a bit late, but here's a chance to submit your application idea, have it judged by a (Mac) celebrity panel, and have it created by a team of hip Mac Developers. It's called "My Dream App". My Dream App (MDA) is a unique contest of sorts, and to date there are over 2300 idea submissions. There's a discussion board so you can float your idea and have it critiqued, as well as general discussion about the MDA concept.
One thing though - you have to submit your idea by NOON August 30. That's like... now.