With high-tech new ways to open the door, now there’s no need to worry about losing your key. At the Sofitel Le Faubourg (; doubles from $1,030), in Paris, guests will soon be able to enter rooms via a radio frequency microchip in their cell phones. But the most cutting-edge system has to be at Boston’s Nine Zero Hotel, where your eyeprint is registered at arrival and a two-second iris scan unlocks the penthouse suite—Mission Impossible style.