Here's another trick:
I have Frontpoint Security installed in my home in The Villages. I've got it set up so that Affordable Homewatch has its own access code to disarm the security system, different from mine. When they enter my home, they must disarm the system with their personal code and I get a text message and an email telling me that they have entered the house, and another telling me that they have disarmed and then rearmed the system. Thus I know exactly how often, and exactly when they visit my home. Thank goodness Affordable Homewatch never misses a week, but if they do, I'll know it.
http://www.frontpointsecurity.com/