You can also get phone cases with bi-color epaper displays on the back! The use case is for photos, but it would be really cool to have an app write notification information to the screen.

Whoa that's clever, just looked it up. I'd be curious to learn more about the power constraints for these- the www.inkcase.com/inkcase-for-... seems to have a battery, maybe it's using Bluetooth or something?

I'm not sure about that one, but the simpler ones I was looking at are powered entirely by the phone's NFC coil. Ones like this, although I first saw the SIXLTR clones reinkstone.com