In Minority Report, the billboards worked like this:
In Tokyo, the billboards are outfitted with cameras that can determine the gender and age group of any passerby who takes a look at them. Even if you just glance at them, the digital billboards only need a second to figure out if you’re a young girl who would like Hello Kitty or an old man who would want a young girl. They promise they’re not recording anyone but they are collecting data to better target those old, so 2009 print billboards.
Welcome to the future where advertisement is disguised as technology. [SmartPlanet]