Or if you've been taking pictures of them through their windows you could post some on their hard drive, just to let them know you're interested
I remember years ago - I mean, like years ago - some TV news correspondent walking down a residential street with a 12yo kid and his laptop, watching the kid latch onto unprotected wireless home networks all up and down the street. If the owner of a home wireless network had a subscription to an 'interesting' website, the kid could book right on in, posing as the owner.