Not within current SDK restrictions. But technically it is quite simple, but the SDK won't allow the files to be saved anywhere except inside the app. Pointless. And plus Apple wouldn't allow it to pass through the app store.
I meant "possible" as in it can be written. If Apple was moronic enough to provide a free alternative to iTunes, they wouldn't be in business right now.
Possible to be written, yes. Inside its little sandbox, thus meaning that you couldn't play the files in iTunes (I know you were wondering for music), so it is possible, but unusable. You would simply have to link the app to the server, give it a few instructions, and build the GUI around it. Simple, but never going to happen in the App Store, and w/o jailbreak, is useless as well.
This would be a great idea for a developer to design for Cydia or the Installer. That way, you would not have to go through Apple and get it in the App Store.
Hmm this makes me wonder, Can a developer create an application strictly for themselves? Couldn't a dev technically just create such an app (or something like it) and use it just for themselves?
You either: a.) Have extremely good hearing b.) Are obsessed with music to a crazy level or c.) Only have downloaded only dodgy songs off limewire because to me, limewire songs sound fine However it would be cool to have this option of limewire app, but you may as well use your computer.. it's kind of like wireless syncing, it just seems almost pointless (tho handy if you lose your sync cable ;P)