1. A method for transferring application state between first and second devices, said devices each including a processor and a display screen, the method comprising: using a camera in a the first device, sensing imagery presented on a display screen of the second device; decoding digital watermark data from the sensed imagery; based on the decoded digital watermark data, identifying stored data that memorializes an application state of the second processor; and using said stored data to initialize the second processor to said application state.