Some embodiments relate to an accessory device that may operate in a first mode, where the first radio of the accessory device is configured to perform cellular communication with a base station, or a second mode, where the second radio of the accessory device is configured to perform short-range communication with a companion device and utilize cellular functionality of the companion device to provide cellular communications through the companion device to the base station. The accessory device may operate to selectively transition between the first mode and the second mode based on one or more factors, such as signal strength of the short-range communication between the accessory device and the companion device, the relative batter level of the two devices, and/or a communications status of the companion device.