I use the online service rdio to listen to music. One of the “features” of the service is that you are limited to a single stream at any given time. If you’re active on one device, other devices display a note indicating that the stream is playing somewhere else, and an option to re-route the stream to device you’re on. But there’s also an option to control playback on the currently streaming device…Remote Control Mode.
The upshot is, you can have Device A driving your hi-fi speakers while you work at, and select new music from Device B across the room. Brilliant.