Well, apparently they've reached a new level with this idea. I'm driving to work this morning listening to the show, and they say that they've installed spy monitoring software onto a computer in order to watch the activities of the suspected cheater. It sounds like it works the same as most, and logs Internet activity, chats, emails, takes screenshots, etc.
My question of the whole thing would be the legal issues involved. Since they're monitoring activity as a third party, what permission do they need? Do they only need permission from the 1 person in the couple to spy on the other? Do you need a Private Investigator license or anything?