If you want to write such an app then go ahead, but I wont be doing it for 2 reasons:
1 - I don't have, nor do I really want an iphone.
2 - If I did have an Iphone there are no real assurances that the software that I created would be accepted onto their marketplace.
Personally, I have a G1 Android phone that has a useful little app called Gmote.
It works via an installed gmote server on your PC (Linux or Windows) and not only lists all your movies, but lets you play, stop, ff,rr etc, best of all it is free.