I don't know if you've ever seen them, but retail signs (like the menu boards at McDonald's, for example) have incandescent or fluorescent lights inside the signs. This makes them easier to see, but it also makes them large, heavy, and bulky.
The solution here is to embed LEDs inside the signs rather than use lightbulbs, and the image above is one example. This results in a much lighter sign which costs less to operate.
This video might explain it better. It shows one of the new signs in use as well as the backside of said sign.
While this isn't anything like what we would call epaper (an E-ink screen, for example), it is still cool. It's a clever adaptation of new technology to replace an old and bulky gadget.
You can see more demo videos on Youtube.