Can you spot the promotional key for the "Lunar Hilton," an imagined hotel on the moon? Hilton's room keys have evolved dramatically over nearly 100 years, from keys to key cards. Today, Digital Key enables smartphones to serve as keys. Hilton introduced this feature of the Hilton Honors app in 2015, allowing guests to bypass the Front Desk and head straight to their room, using their phone to unlock their door. Hilton has 4,100+ properties around the world with Digital Key and our guests have opened more than 40 million doors and counting since Digital Key launched.