Embodiments help to provide a cross-device security schema for an audio device and a master device to which it is tethered (e.g., a smartphone). An example security scheme provides flexible mechanisms for locking and unlocking the audio device and the device to which it is tethered. For instance, an example security scheme may include: (a) an unlock sync feature that unlocks the audio device and keeps the audio device unlocked whenever the master device is unlocked, (b) a separate audio device unlock process that unlocks the audio device only (without unlocking the master device, and (c) an on-head detection process that, in at least some scenarios, locks the audio device in response to a determination that the audio device is not being worn.