Here is a cool flip cover for smartphones with an e-paper display and a pressure- and bend-sensitive input sensor that lets smartphone users do more with their phone. It can be used to perform various touch, pressure, grip, and bend gestures. The secondary e-paper display lets you view maps, books, and other content from the main display.
FlexCase has Book, Laptop, and Backside modes for augmented interaction with a smartphone. The above video shows what you can do with something like this.