E-Ink, the display technology found in Amazon's Kindle and other popular eReaders, is most interesting in that it is a static display technology. It doesn't require any batter power at all to display the content. It does require a little bit of power to change what's displayed, but once the “paper” shows a new image or set of text, it'll stay there pretty much indefinitely.
Since owning a Kindle, I see signs all over my world that I think should be E-Ink. Basically any large signage that is currently printed up on big boards, but needs to change periodically.
- The pricing signs at gas stations
- The “lifeguard/no-lifeguard” signs at swimming pools
- The “no vacancy” signs outside big hotels
- The “today's events” displays in hotel lobbies
All these signs today are analog paper, which means they still have to have lighting, and someone come by to change them every day (or more often). And as an added benefit, for signs that are in an awkward location, you could imagine that a worker comes along with a battery pack and small hand-held device, providing enough power to alter the signage, then walks away. With no vampiric power-draw, you've save energy, and it'd be safer (think around a pool, where you don't want a powered device in case the humidity or splashing cause it to short out).
I'm assuming that the delay on this sort of thing has to do with the price and ability to manufacture large-format versions of E-Ink displays, but you have to think it's coming.