This umbrella from Gizmodo has a handle that changes color based on weather forast the umbrella receives through a Wi-Fi network. I think that's where billboards may be heading. Billboards can be updated with new info depending on the context - weather, day time, traffic. Equipped with with motion sensors or face recognition thingies, they could feed real-time stats back to the propaganda headquarters. They could even pass info to each other. I wonder if this kind of tech already exist (Japan, maybe?). If you know of any, leave a comment or shoot an email.
