Abstract: Systems, methods and non-transitory computer readable media for allowing a user to switch between watches that have been paired with a device such as a smartphone are described. In one embodiment, the watches automatically detect a removal of a first watch from a user's wrist and an attachment of a second watch to the user's wrist. Messages from the watches are transmitted to the device to allow the device to switch the active watch from the first watch to the second watch. The switch can occur while the device is in a locked state, and the device can synchronize the second watch with data received from the first watch. Other embodiments are also described.

Abstract: Systems, apparatuses, and methods are provided that can reduce problems associated with updates of various applications on various devices, including addition of new services for communicating with another device. A compatibility version (e.g., a minimum compatibility) for a first communication service on a first device can be checked against a compatibility version for communication service on a second device. A comparison of the compatibility versions can determine whether a message can be sent using the first communication service to the second device.

Abstract: When a new version of a first program is to be installed on a first device, metadata supplied to that device specifies which versions of a second program stored on a second device are compatible with the new version. The first device uses this metadata to determine a compatibility classification that indicates how compatible the current version of the second program and the new version of the first program are, and transitions to a state representative of this compatibility classification. A process executing on the first device receives messages from applications executing on the first device. The process reads mappings between these applications and the message types these applications send. The process forwards an application's message to the second device if the application sends a message type allowable in the first device's state. Otherwise, the process queues that message at least until the first device transitions to a different state.