Just an FYI +1 for this!
(e.g. I use BubblePNP app for Android, and can push/render playing music sourced from my NAS (stored as FLAC), from my tablet or phone to each other, to XBMC on the laptop/TV setup, to the Xbox.... The only thing missing from the setup being perfect is being able to render it to MusicBee.
Sure, I can push it to XBMC/or Media Center. But I MUCH prefer MusicBee. Also to push to them it uses the hdmi connection to the TV speakers, and I'd have to change the source every time to switch to using the Hi-Fi setup speakers. Just as an outline of why it would be bloody awesome if UPNP was integrated.)