The US Patent and Trademark Office has awarded Apple a patent on the "Slide to Unlock" gesture used on iOS devices. Wording in the document refers to unlocking "if contact with the display corresponds to a predefined gesture for unlocking the device," using certain feedback cues as necessary. Specifically, though, diagrams depict a rough version of the slidebar seen on the iOS lock screen.
The patent is credited to Apple's senior VP for iOS, Scott Forstall, as well as engineers Imran Chaudhri, Bas Ording, Freddy Allen Anzures, Marcel Van Os, Stephen O. Lemay and Greg Christie. Of special interest though is that a patent application was first submitted in December 2005, well before the announcement of the first-generation iPhone in January 2007. This suggests that even some minor iPhone concepts had been cemented long before the the device would ship in mid-2007.
Other mobile device makers have taken to using alternative gestures for unlocking. Some Samsung phones, for instance, ask users to "wipe" a lock screen off, or insert a puzzle piece. HTC's Sense 3.0 and 3.5 interfaces require users to pull a ring.