Have you not heard of heroin chic? Look this technology will be proliferated but in a different context. At some point the integration of keys and other objects will be common place. Its not only car makers that are looking into this but cell phone companies in particular. Aston integrates its key with a watch. The only technology that matters is the one that sells even if its pointless.
But you see, an Aston Martin key integrated to a watch is good (given that the watch is any good obviously), that removes your need to carry your car keys at all, all of it's functions have been integrated to perhaps a few buttons on your chronograph or perhaps even totally free of buttons. And you'll have your watch with you all the time anyways. So that makes perfect sense. Eliminate car keys, integrate them into something that customers will have with them at all times.
Now you might obviously say that watches aren't something everyone tends to carry with them, well, i'd still say that about one in a thousand customers of Aston don't have a watch. In econoboxes that thinking wouldn't necessarily work so well, since us young people (and old ladies maybe) aren't supposed to be so much into watches anymore, apparently we just check the clock from our cell phones, but just as their Aston Martins, AM (and any other prestigious car for that matter) owners own watches as status symbols, and they carry them all the time. I (and plenty of my friends) however use a watch, and don't plan on giving up on that anytime soon either, so it isn't doomed in econoboxes either, just not as good an idea.
The idea of integrating other functions into something that most people don't carry unless they need it for it's primary function, on the other hand, is rubbish. It would be possible to integrate plenty of functions into a screwdriver or a hammer, that could probably be our (legit) electronic car key or credit card or MP3 player, but why hasn't anyone built such a thing? Because most people don't carry a screwdriver or a hammer with them, unless they'll need it for it's primary function, turning screws or smashing nails into walls. The same goes with car keys. Why integrate something non-car related into a car key, because it's not likely we'll have them with us unless we actually need them for opening our car doors and turning the engine on or off?
And i can't see that being a smash hit on the sales front either, since i reckon that most people who can afford new BMW's are at least moderately affluent, and therefore have some financial sense. And according to my financial sense, double charging isn't something i want to pay. I don't want to pay my monthly fees to BMW for using their key as my credit card (which i bet they'd charge, it's BMW, remember), unless that eliminates me from a larger or equal fee, charged by American Express, Visa or other credit card company for using their card, which i can't see it doing. Therefore i'd rather use cash, or should i need a card, just a card, for which the provider of the card charges me a monthly fee for.
This is actually visible right now from the car manufacturer's branded credit cards. Edmunds featured an article on them a long while back (i'm not sure if they still have it on their website), from which it was clearly visible that the fees increased as the car manufacturer with their car-related benefits came along. And well, rather obviously, the luxury manufacturer's fees were fairly high, higher than "run-of-the-mill" manufacturers, and at least i missed what made them so expensive in the first place. Obviously you could get discounts on car-related services through the card, but then, you can get benefits with (especially the big-spender) credit cards anyway, if not necessarily from car services, but maybe from hotel nights or flights or whatever. So in my opinion, much of the added (perceived) value actually comes from the brand value (or badge snobbery, whichever you like more). And is brand value worth paying for in this case? Not in my mind.
Wow, this became one long post.