It's just a concept for right now, but three designers at the "Innovation Unit" of the Royal College of Art in London have created a design for concrete that can double as an information display. Called Chronos Chromos Concrete, it's basically concrete that's mixed with thermochromic ink and with nickel chromium wires installed right below or behind. When you want to display specific words or information or whatever you just heat up the right wires and they cause the concrete just above or in front to change color. Sounds like it's a long way off from commercialization, and the worst part is that if any of the wiring breaks you have to bust out the jackhammers to make repairs.
[Via Near Near Future]