Who carries an iPhone without a case? Ok, well I don't because it's too expensive and/or a hassle to replace even with AppleCare. Based on this ad you must place your phone directly against the door's receiver. This means I'm required to pry out my phone each time I enter the room and that's in itself kills the convenience.
I am waiting for the day when they make doors that will recognize a guest in such a way that the guest will simple be ported through the door without opening the door, pulling anything out of his pocket, etc. Until that day comes I can't be bothered with using my iPhone to bypass the front desk and not have to deal with those useless key readers.