The Rocketboost system at best buy is a wireless solution that will work for you: http://www.bestbuy.com/rocketboost gives a good summary of how it works.

You can add speakers and audio sources around your house, and the speakers have a "next source" button that lets you flip between your audio sources. It is modular, where you can buy as many units as you need and they all join together into one big network in your house. It isn't super-cheap, but it is cheaper than other products that are equally as flexible in how you set them up.

Disclaimer: I worked on this product (wrote the protocol stack for moving the audio data over the air), so you may want to take my recommendation with a grain of salt, but I am happy with how well the product turned out and I think it's pretty neat.