I notice that the cards consume electricity. I wonder how long the battery lasts, and how they're replaced. Furthermore, there's the whole pressing against your

I notice that the cards consume electricity. I wonder how long the battery lasts, and how they're replaced. Furthermore, there's the whole pressing against your card, and looking at the actual pressing action, it looks like you have to press them pretty hard (or maybe he just was). How durable is the card, really?