Two choices here. A wireless RF based Ir repeating system like the x-10 Powermids, or a much more reliable hardwired system from Xantech or someone similiar.

This is truly a case of you'll get what you pay for. In some homes the Powermids work fine, but in most homes, they will be subject to interference from lots of sources, and only be about 85-95% reliable. That may sound like a good reliability rate, but you'll get tired of it quickly.

The wired systems are harder to install, but you can count on them being just about 100% reliable.

Here's a couple of links:
[Link: smarthome.com]
[Link: smarthome.com]