Device accessories including cases are fairly common to see these days. But every once in a while there is one that has a stand-out feature. In this instance that stand-out feature just so happens to be an e-ink display. The case is is from PocketBook and for the Samsung Galaxy S 4. Basically, what you have is a flip-style cover that when opened, has a 4.3-inch e-paper display.
This cover is similar to the official Samsung flip covers in that it has a replacement back cover for the Galaxy S 4. Otherwise, the hinge is made of fabric and again, similar to the Samsung flip covers, there isn't anything that keeps the case closed. Needless to say, the idea is simple, you can use the PocketBook e-reader app to send text from the Galaxy S 4 to the case.
This should be good for simpler text and perhaps key -- it should also use a bit less in terms of battery life. Touching back on the PocketBook e-reader app. This one has a drop-down menu that will allow the user to send the text over to the e-paper display with a simple tap of the "display on eINK cover" option.
Once the text has been sent you can fold the case over the back of the phone and the regular Galaxy S 4 display will turn off. This is where the using less battery life aspect comes into play. To stop using the case you open it back up and from the drop-down menu, hit the "close document" option. One drawback to the case is the support, at present you can only send text using this official PocketBook app.
That all being said, this looks like an interesting idea and one that could be useful for those who often find themselves killing their battery life by reading. As of this time we have yet to see any details in terms of pricing or availability.