Might happen sooner than later according to this article
I would welcome (practical) innovations beyond the plastic key card everyone uses these days. Very few things annoy me more than checking into a hotel, making it all the way to my room, and finding out the card isn't properly magnetized.
Why not an iphone app - having the key in my pocket just gets wiped out by the phone anyways - this would be a great marriott idea
some have already done that with the smart phones.