Alternative to wireless network - use the mains

I was looking into how to include a computer located in an outhouse, into the home network. The computer is too far from the wireless access point to use wireless and running a CAT5 cable was something I was hoping to avoid. The outhouse has mains power and I came across devices which allowed you to extend your home network via the mains cable. There is a review of one such solution at ADSLguide:-

http://www.adslguide.org.uk/hardware/reviews/2003/q3/phonex-neverwire14.asp

The devices there seem expensive and a google search soon found cheaper options. Might be suitable for other people thinking of sharing their broadband connection around the home but not wanting to learn up about wireless networks and security.