"Paper Four" -- Interactive paper

Researchers at Mid Sweden University are garnering some press for their newly-developed interactive paper. According to the research homepage, the paper is a "touch sensitive printed surface".

While I was initially less-than-impressed by the fact that it's 3cm thick, it looks like that's simply a mounting choice and not a requirement. The NewScientist article mentions that it's a layer of paper printed with lines of conductive ink that's used to do the sensing. If you were to combine this with an e-ink / e-paper display and some printed circuitry and could start manufacturing electronic devices almost entirely of paper.

What I'd love to do is take something like this and augment my paper wallet with a built-in PDA..