Fuji Xerox has just demonstrated what may be the Holy Grail of e-paper—probably not the "E-Ink" technology found inside the Amazon Kindle and Sony Reader, but something similar—a prototype display that a user and write on. Three layers of polymer-dispersed liquid crystals are used (red, green and blue), meaning the display has a gel-like base.
Still flexible, the display can recognize "optical" writing, though probably not quickly. An eyes-on report mentions that the refresh rate is under a second, which while probably fast enough for quick marks, is not what you want to be handwriting a letter on. But we just had our boobie doodles in mind anyway. [techon]