Electronic ink displays are not very expensive to manufacture, not that much more expensive than normal paper, yet the cost of devices containing them is quite high. That is because of the control circuitry that drives the display. I envision an application that does not require such circuitry - small notes with a low-tack adhesive or even full sheets the size of an ordinary piece of notebook paper, that can be "writen on" and "erased" with a plastic stylus containing two magnets.

The eraser end of the stylus would be a larger magnet polarized to repel the ink away from the surface, while the writing end would be a smaller magnet polarized to attract the ink to the surface where it is visible.

Many uses of paper involve temporary storage of information (text, an image); once the information is used or transcribed the paper is discarded. These reusable notes would save paper, as well as the plastic and ink used in normal ink pens. If a mistake is made, rather than scribbling out the error and writing the correct information the error can be "erased" without unsightly marks or wear and tear on the surface.

Combine this with a digital camera and possibly optical character recognition software and reams of notes can be taken and efficiently stored using very little in the way of physical resources.