Hilton Worldwide introduced a mobile app that lets guests use their smartphone as a room key.

The smartphone-based keys use Bluetooth technology inside the handsets to unlock the doors, and require the user to open the app and put their phone next to the panel of the door. If the user doesn’t have the app or the phone, he/she can get a traditional key card from the front desk.  

Hilton’s Digital Key is available for HHonors loyalty members. By early next year, the feature will be available at 250 U.S. hotels operating under the Hilton, Waldorf Astoria, Conrad and Canopy by Hilton brands, the company said.

Hilton started beta-testing the feature at the Hilton Alexandria Old Town in Alexandria, Va., earlier this month.