>Thanks, that would be very interesting. The e-ink one should be very light and work on one AAA battery for weeks. :)

Maybe I'm thinking of something different than eInk, but I don't think it requires batteries. What I've seen (not in person, only on TV), was paper thin sheet that was more or less an etch-a-sketch. Xerox had been developing it and planned to use it for store signs pretty soon.