The Sonos Controller for iPhone download, available now from Apple's App Store, turns the players and phones into a virtual facsimile of the Sonos ZoneController.
Users can "quickly link and unlink rooms without interrupting music playback, select Play, Pause, and Skip in any room, search for favourite artists and songs by typing on the touchscreen, and browse a collection by pointing and flicking."
You can see a demonstration of the Controller in action here (opens in new tab).
Also available as a free download is Sonos 2.7 System Software, which is required to work with the iPhone controller.
Additional features of the 2.7 release include "support for a suite of music content including Last.fm streaming and scrobbling and free access to more than 15,000 radio stations and shows from around the world."