Sonos for iOS adds direct device streaming, takes PCs out of the equation (hands-on):

"Sonos has been steadily reducing our dependency on the computer as the cornerstone of its multi-room audio system, but there's been one link left to cut: local music. Outside of an AirPlay workaround, a PC of some sort has always had to stay awake to stream a personal collection. If you're an iOS user, it's now possible to go truly PC-free. A 3.8.3 update for Sonos' apps plays music stored on an iPad, iPhone or iPod touch directly through the system, with no hoop-jumping required. Local content is put on equal footing with pure internet sources, too -- the software can mix local tracks with those from Amazon Cloud Player, Spotify and other internet services as part of the same playlist. There's no official word of direct device streaming for Android, although we wouldn't be surprised to see it follow before too long."