If you already have a ton of music on your PC, you can access them all seamlessly with Didiom. They play as if they were on your phone!
Doesn't help if you don't already have a bunch of music though!
Actually, I take that back. They do sell songs too. But I just use it for free to stream my PC music.
It is capable of streaming music from itunes, but does not require the songs to be from itunes to stream. Just so that's clear. They just wanna make it known that you can stream your protected itunes songs too!
http://www.didiom.com/