From Scientific American:
In many rural areas of India, schoolchildren use chalk to write on handheld, erasable black slate tablets roughly the size of a piece of paper, because their teachers lack the funding or electrical infrastructure for anything more sophisticated. A group of humanitarians and educators are trying to change this by developing a new type of solar-powered LED tablet, called the I-slate, that uses a stylus rather than chalk and features a special chip that uses up to 30 times less electricity than a standard computer chip.
How do they make the slate so power efficient? They are using a processing chip that leverages probablistic rather than Boolean logic (PDF).
Of course, displays often use a large chunk of power too, so it’ll be interesting to see what’s done here.