Some disclosed devices include an inertial sensor system, a proximity sensor system, an antenna system configured to transmit and receive radio signals and a control system. The control system may be configured for receiving inertial sensor data from the inertial sensor system and controlling the proximity sensor system and/or the antenna system based, at least in part, on the inertial sensor data. In some examples, the control system may be configured for controlling the proximity sensor system and/or the antenna system based, at least in part, on whether the inertial sensor data indicates that the device is being held, is being carried or is on a person's body (e.g., is in the person's pocket).