TUAW is told that a media navigator will allow you to view videos, play podcasts, listen to music and even support shuffle playback. The screenshot shown here shows some of the localizable strings for the iPhone-based application. There's obviously no timeline for release, but since the SDK event back in February, it's been rumored that Apple would release some official iPhone apps of their own, and iControl might be the first.
Update: The data is so thin on the ground that it's hard to respond to readers who have asked whether this will be a "Back to my iTunes" application. Just having local Bonjour support wouldn't be all that useful. Apparently a screenshot of the bundle (not apparently a real application) here