In the music app, there is a Connected Media tab. It shows up my router, a Belkin Play Max, but it does not show up my NAS device, which has an iTunes server and a "Media server" of unspecified protocol (at least it's not stated anywhere in the web interface). Neither of these show up.
What does this tab connect to?
EDIT: The device is the Desire HD running Android 2.2 as installed on it by default.