@ helios: You mean log their spouses keystrokes? I agree, it is a shady thing to do even during divorce proceedings. You'd think they would target a larger market that would need this kind of service more; like government sector employee's with access to financial information or even just sell straight to PI's.
Then you ask them. The longer a couple is together the worse they are at lying to each other. It's a combination of the liar feeling stressed and the other person learning their tells.