by Michael J. Shapiro | March 01, 2010

It's already difficult to find something a cell phone can't do; soon, it might also open doors. "Our application works with all cell phones, anywhere in the world, with all carriers," says Paris-based Pascal Metivier, founder and CEO of OpenWays. The company, a provider of mobile-based access-management and security solutions, unveiled an application last November that will allow hotel guests to open their room doors using Crypto Acoustic Credential technology -- the same concept behind fax machines.

Each room "key" is a unique sound, says Metivier, used only once. At the check-in desk -- or remotely, if the hotel allows online check-in -- a phone number is transmitted to the guest's phone. The guest calls the number while standing in front of the room door, and the phone emits the unique sound that opens the lock. (Hotels must install a receiver compatible with most major electronic locks.)

Travelers might be seeing this environmentally friendly application soon: According to Metivier, "some major hotel chains" intend to unveil pilot programs this year.