Well, it happened - the slide-to-unlock patent Apple has been requesting was granted this morning by the US Patent & Trademark Office, meaning almost any device in America using a sliding unlock mechanism is now infringing on Apple's patent unless otherwise ruled.
While the timing may seem a bit suspicious, Apple originally filed for the patent in 2005. Have a look at this excerpt from the granted patent document:
A device with a touch-sensitive display may be unlocked via gestures performed on the touch-sensitive display. The device is unlocked if contact with the display corresponds to a predefined gesture for unlocking the device. The device displays one or more unlock images with respect to which the predefined gesture is to be performed in order to unlock the device. The performance of the predefined gesture with respect to the unlock image may include moving the unlock image to a predefined location and/or moving the unlock image along a predefined path. The device may also display visual cues of the predefined gesture on the touch screen to remind a user of the gesture. In addition, there is a need for sensory feedback to the user regarding progress towards satisfaction of a user input condition that is required for the transition to occur.
Sounds fairly nebulous, right? It's unclear to me whether this description fits either Honeycomb or Ice Cream Sandwich's lock screens, but it certainly sounds close to Android's current default lock screen, and, given Apple's penchant for going after Android and its manufacturers, we can probably expect to see some interesting developments in the near future. You can see the full patent on the US Patent & Trademark Office's website here.
It's worth noting that Apple won a similar patent in 2010, which focused more around animations, including the lock screen and letter pop-ups on the iPhone's keyboard. Today's patent is essentially an extension or clarification of 2010's patent, related more specifically to the method used by the unlock screen.