A mobile device, particularly a wireless headset, includes a cord to which an earpiece is fixed and a module having a spring-actuated retractor reel into which the cord is retracted for storage. A fastener on the module makes the device wearable. A rotary encoder generates a position data output according to the rotational position of the reel, and a controller receives the position data output from the sensor, and, in response, controls a function such as placing the device in an on-hook or off-hook state.