Advertisers are developing digital posters that will recognise people's faces and respond by flashing ads that are according to their tastes.
The technology is so sophisticated that it could soon even be possible to link the posters to a store's profile of each individual and display goods that would appeal just to them.
The posters recall the famous scene in the 2002 science-fiction thriller 'Minority Report', in which Tom Cruise walks past a row of digital signs which scan his retina and display holograms of products that he likes.
The technology can also recognise subtle facial expressions, such as a raised eyebrow or a frown.
As the billboard cameras become increasingly sophisticated they will be able to recognise more telltale signs that could pinpoint the type of consumer each passer-by is.
The company paying to advertise on the virtual billboard could then tailor a specific product to the passer-by accordingly.
The scanners also pick him up when he enters a Gap store and show him an image of a woman selling him clothes.
So far the most advanced posters allow shoppers to see what clothes would look like on them by superimposing the items on a digital picture of themselves.
Interactive advertising agency R/GA has already put a series of such devices in the children's section of U.S. clothing retailer American Eagle Outfitters, but it hopes to take them far further.
"What we are trying to do is figure out what your brain is doing," the Daily Mail quoted Benjamin Palmer, chief executive of advertisers Barbarian Group, as saying.
"If your eyes are the windows into the soul, we're paying attention to what you are paying attention to," he stated. Barbarian hopes this summer to introduce billboards, which respond if you are paying attention, but other executives have spoken of developing technology that "actually recognises faces".
"If you want to do something evil with it, I'm sure you could. It is the same thing with anything else technology-wise," Palmer added.