[a9h74j]

I've imagined having an OLED screen which only flashes on momentarily. Could be used for writing without editing.

[Aloha]

I've imagined like an OLED/ePaper hybrid for that application.

[404mm]

Or e-ink display. Unfortunately those are quite pricey compared to LCD

[shaunsingh]

rLCD is probably more effecient, and much more readable under good light, the memory lcd in the picture also has epaper-like retention capabilities.