Also, you could make the card thicker in areas where it doesn't matter (away from the stripe and the PIN
(imagine this card getting stuck in an ATM, suddenly all your cards are lost)
But if they can do that, I want one, not to pay with, but for the programmable eInk screen with bluetooth connectivity (and touch? get real).
Then I'd hook it into my phone, that would somehow detect who is nearby/looking at it, reverse/stalk their social networks, local graph, location/environment context, little bit of magic, cold reading and random guesswork.
It would show exactly whatever they wanted/expected to see.
I'd have hacked myself a piece of Doctor Who's psychic paper.
[0] or at least for a few years :)