I like that. Maybe with the leaps forward they are making with miniaturization, they could have a credit card sized thing, that stores many keys, can read your thumbprint, and has a built-in mini-keyboard for entering passwords on the card. Looks like the guy testing this Electronic Paper is trying to hide his thumbprint. :-)
I was thinking a USB or Bluetooth connection to the hardware versions. One with its own miniature keyboard could come in handy in a pinch, though. I tend to use KWallet or something similar on my PCs already.