SpyMeSat is a clever US$1.99 iOS app from Orbit Logic Incorporated that lets you know when you are in range of an imaging satellite that might be snapping a picture of your location. You can see details on what imaging satellite is overhead, plus a map that updates a satellite's location in real time and a picture of what it looks like.
You can configure alerts to let you know when the satellite is nearby. The details of what a particular satellite can see are quite interesting, with some of the satellites having resolution of about one meter. That makes for a pretty detailed view, though I suspect classified satellites can do even better.