Multiroom Audio:

"Some of the brands we use include: Nuvo, Aton and Apple AirPort Express."

What it does:
Distributes different music sources to different zones, amplifies and plays them out on in-wall or in-ceiling speakers. Controls each zone from an in-wall keypad or wireless handheld controller.

Retro Fit:
Nuvo's P100 & P200 use standard WiFi networks to stream music wirelessly to multiple zones/rooms as does Apple's Airport Express making multi-room retro fitting a breeze.