Around here in a case like this it is probably done by someone you know. Have you had any work done on your house recently? It might be one of the contractors employees. Have you taken your car to one of those quick oil change places? If you did they may have noticed the GPS unit and then got the address of your house from there buddy that works there and used it to watch your place waiting for you to make a mistake. Do you have children? It might be one of there friends. These are some of the things to think about.