Ever hear of the X-10 line of home automation products? It's been around for a very long time. I help a neighbor install some crappy security cameras once, which ripped out a month later, and paid a proffesional to install some overpriced video system. The on/off functions were through the outlet, while video was still the basic wireless. Really filled up the outlets, must have had a dozen wallwarts going, monitor, VCR...
Anyway search for "X-10", the company site will tell a little about how it works, but not enough to get you to build your own. You should get thousand of hits, relating to home built devices and a deeper explaination of how it works, and how to do it yourself. Might even find the sort of device you are looking for. You didn't really give any detail on what kind of comunication you were after, but guessing voice. There are devices which allow you add a telephone jack through your house wiring, but don't remember the company. As far as going outside your property... don't recall seeing anything like that, would think your signally would quickly pick up a lot of noise, or get filtered out.