E-paper displays are new innovative commercial displays that resembles ink on paper, requires ultra-low power, and can retain the image displayed even in the absence of power. Frank Buss‘ entry to 2017 Hackaday Prize contest is a solar-powered e-Paper display driven by ESP32/ESP8266 and a sticky magnet on back that can be used as a sticky note on a fridge to display important information over WiFi.
The amazing thing about ePapers is that the image lasts without power forever (I tested it for months), and the contrast is very good. The idea is to build a small device with ePaper and solar cells, and then you can write or draw on the it with your smartphone, or even remotely from anywhere over the internet to show a message. The case will have magnets on the back to stick it on a fridge or other metal objects. It will use an ESP32, which polls a server once per hour to get a new image to display.
This is the electronic version of sticky notes. But the ability to update it over the internet opens up many novel applications. For example install it on the fridge of your grandma, who might not be very proficient in using modern internet connected devices. Then you can send her birthday wishes, or remind her of schedules. And the buttons could be used as a feedback channel, like confirming a date. Or when installed at a public place, it can act as a bulletin board. Or it can be used for a modern form of internet connected graffiti or other art projects. The possibilities are infinite.