Something else to be aware of, is the fact that portable home phones are easily picked up on any police scanner that can be bought at places like RadioShack.
My brothers good friend caught his wife cheating on him, and when it looked like she might get the kid, and eveything else, he caught and recorded her off of a police scanner while she was talking with her new boyfriend on a portable phone. He played it for the judge (there was a long conversation recorded that let the judge know just what she had been doing, some of it lies told to the court about things she claimed he had done to her), who, upon hearing it, awarded him custody of the kid and most of his belongings.