Powerine Carrier Technology, also known by its trade name HomePlug, distributes stereo music and control signals throughout your home via your home's existing electrical wiring. PLC makes it easy to have a multiroom audio system without installing any new wiring in your home. There are do-it-yourself systems, such as the IO Gear Powerline Stereo Audio System, which are mostly plug and play. The IO Gear system consists of the Powerline Audio Station, a base station with a built-in iPod dock and a Powerline Stereo Audio Adapter. The Audio Station is placed in the main room and the Audio Adapter in any other room in your home where you want music. Read my full review of the IO Gear Powerline Stereo Audio System.
More advanced systems and components are available or in development from Russound with the Collage Powerline Media and Intercom System, which consists of an amplified in-wall keypad for each room with 30-watts of power (15-watts x 2)and a small full-color display. Each control keypad has an FM tuner and a Media Manager that connects the system to a home's Ethernet network for sharing content between zones. A pair of in-wall speakers would be installed in each room. Read my profile of the Russound Collage.and learn more about the system.
NuVo Technologies is working on the Renovia, planned as a 6 source multiroom system for as many as 12-zones or rooms. Audio sources will connect to a Renovia Source Hub, which includes built-in AM/FM tuners, and satellite radio tuners. Additional sources, such as a CD player can also be connected to the Source Hub, for a total of six sources. Read my profile of the NuVo Technologies Renovia.
The Collage and Renovia systems are aimed at the retrofit installation market - homes where installing room-to-room wiring is not feasible or too expensive. Both systems need to be professionally installed. Read more about how to select a contractor.