You've probably figured this out already but this plays a movie, or mp3 from a server but I am not sure it fits your definition:
-(NSURL *)movieURL
{
if (mMovieURL == nil)
{
id path = @"http://www.yourserver.com/iphone/yourmovie.m4v";
mMovieURL = [NSURL URLWithString

ath];
[mMovieURL retain];
}
return mMovieURL;
}
(I got this from another post - not my code)
I have not tested this on an iPhone but only on the simulator so I can't comment about performance issues.
One thing I don't like, when playing mp3 it displays a Quicktime logo and the url of the file. I would like to be able to define an image to use as a background or minimize the instance of MPMoviePlayer so I can show and image.
My only solution thus far is to create a slideshow of images as a movie and just treat it as a movie but that increases the size from a 6Mb sound file to a 84Mb movie file... all for the sake of images.