1. A portable electronic device, comprising: a touch sensitive display; memory; one or more processors; one or more programs stored in the memory and configured for execution by the one or more processors, the one or more programs including instructions for: displaying a first unlock image and a second unlock image on the touch-sensitive display while the device is in a user-interface lock state; detecting a gesture on the touch-sensitive display; transitioning the device to a first application corresponding to the first unlock image if the detected gesture corresponds to a predefined gesture with respect to the first unlock image; and transitioning the device to a second application distinct from the first application if the detected gesture corresponds to a predefined gesture with respect to the second unlock image.