Remember the scene from Minority Report where Tom Cruise is on the run through a shopping mall, and all the signs interact with him because they can biosense his identity? It is a very effective envisioning of an intrusive database society of the future.
While the personal identification is some time off, you can get pretty close even today with Human Locator. A camera/software combination picks out the body shapes and positions of people in front of e.g. a store window and integrates with computer generated window displays so they can react to street movement outside:

The Human Locator analyses a camera feed in real time, sending detailed information about people's location, size, and movements. This data is then used as input to control projections, video, graphic animations, and sound.

Et Just tip