I don't see any flexible mobile phone infront of me.

What I was thinking about is a "normal" hard phone with a "normal" LCD/OLED display in "normal" pocketable size. But where you can draw out a tablet-sized non-lit display. Consider a pocket-sized phone with an optional 10x20cm (4x8") extendable display.

A big problem with todays smart phones is that the display is not working for people with impaired vision. The displays are getting larger, but at the same time getting higher-and-higher resolutions. A person who breaks their glasses may be totally unable to figure out how to call an 112/911 alarm number, because they can't see how to find the phone application or the buttons of the virtual keypad.

An alternative is to integrate a projector, where flat and neutraly colored surfaces may be used. But a problem with a projector (unless a laser projector with very thin beam) is that it needs to be focused. So changing the distance betwen surface and phone will both change the size of the image, and will also make the image blurry.