At Intel's Develop Forum last week, the company showed a prototype laptop with a secondary outer E Ink panel. The E Ink display seems about 4-inch in size and is black and white as you can see in the image below:
Intel says that the first idea came from laptop stickers - so you can use this display to dynamically change what you show on your laptop case. In addition, Windows laptops have a very low power mode called connected standby - and in such a mode the E Ink display can be used to show notifications, news, etc - as the display is very power efficient.
Intel plans to show reference two-screen laptops and ship them to PC makers next year, and they will also provide a software development kit for the E Ink display.