In response to determining that devices 10A and 10B are adjacent (e.g., in response to detection of adjacency by the control circuitry and sensors of either device 10A or device 10B or both and/or confirmation using other adjacency detection/confirmation mechanisms), devices 10A and 10B may transition to a joint operating mode (block 64). The transition to joint operation may take place automatically or may proceed in response to user confirmation by the user of device 10A and/or the user of device 10B that joint operation is desired and authorized. As an example devices 10A and 10B may display an on-screen interactive prompt asking each user (e.g., if there are two users) to enter a password and to confirm that joint operation is desired. Devices 10A and 10B may then proceed to operate in a joint operating mode, as described in connection with state 50-2 of