I've started working on such a project, but it won't be a card, at least not the early models. Only items 1 through 3 in your list are really critical here, at least to start. Also, a display built into the unit is absolutely critical. Without it, there can be no security at all.
Interesting, I would be interested in knowing more if you would be willing to share; as for your display statement could you elaborate on the assumptions around that