You know, these automatic optics + digital technology cameras the sattelites are equipped with can take precise pictures of cities, streets and even houses, when the weather isn't cloudy and the satellite is close enough to the atmosphere.
My idea is that automatic espionage can be done by sattelites. A photo of a certain person taken from above could be transmitted to the sattelite, then it would be optically processed and used for keeping the track of this person's relocations. It has many limitations: 1) only day-time; 2) only outside the buildings an vehicles and 3) only when it's not cloudy.
However in some cases it could be very useful. Before the technological progress allows constructing cameras of such a precision, this idea can be used as a plot for a Hollywood movie.