My dad has one of these set-ups to keep his retarded Basset Hounds in his yard. From what I understand, he has a rod at each corner of the property and a electrical current connects them together. His dogs have a collar when draws that current the closer they get to the invisible line. 
I think he said it cost him $2500 bucks or maybe a little less? I put up a 6' wooden fence cheaper then his fancy high tech thing. 

 His yard is about 1/2 a acre bigger then mine though. 
He says it works good...but it should for that kind of money.