I'm pretty sure nfc can be passive, the e-ink display doesn't use energy when not changing, and the "touch screen digitizer" could just be a button that is actually a contact (i.e. most of the time the microcontroller is passive).
Also, you could make the card thicker in areas where it doesn't matter (away from the stripe and the PIN
You can't, actually. Consider things like the ATMs that suck in the entire card, or things like Metrocard vending machines that require you to insert the credit card in a slot.
Really good point. I doubt they'll ever[0] be able to put all that tech into a card that's actually as thin as a credit card that fits in an ATM.
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.
Also, you could make the card thicker in areas where it doesn't matter (away from the stripe and the PIN