Hehehe...don't get me wrong, I'm PERFECTLY happy with the mag stripe keys currently in use (of course, some would say I'm biased since I collect them lol), but since it seems like technology wants to push forward, RFID seems more likely than any audio implementation. When reading of audio keys, naturally I flashed back to Cap'n Crunch and the phone phreaks back in the 70's...and all of the tone related "activities" subsequent to that little whistle.

It will be interesting to see how testing of the audio keys works. I can't imagine standing outside my hotel room door, getting out my phone, calling the hotel, then "the computer-generated tones are sent to mobile devices and played outside of guestrooms" - I assume meaning that my phone rings, I answer it and the tone is playing as I hold it up to the microphone located near the door. Seems to me it's a LOT easier to just swipe the key and enter. I really don't want to hear phones ringing in the hallway all night long as guests are entering their rooms.

RFID does have significant security issues as you mentioned that can (apparantly...which is a dangerous word when associated with security) overcome through various means such as crypotography but with added costs. Such additional costs seem silly when given the simplicity of the mag stripe key. Back in my phonecard collecting days, I also collected prepaid gas cards and watched the Mobil GO card program disappear in favor of the Mobil Speedpass fobs which used RFID technology and some form of cryptography. I guess since those days, I always fear that somehow fobs will rob me of my beloved cards

While staying at Aria before Christmas, I have to admit that the RFID technology also bothered me as I didn't want them detecting the multiple Aria keys I was taking from the hotel. I somehow pictured myself as a blip on their "radar" packing a boatload of keys in my suitcase

Jim