An electronic device that selectively performs a predefined action is described. The predefined action can be any action performed by the electronic device, such as changing the power state of the electronic device or a component, change the state of a display, initiating a process, ending a process, etc. During operation, the electronic device may transmit a wireless signal. Then, the electronic device may receive a wireless-return signal associated with an object, which can indicate a time-of-flight of the wireless signal between the electronic device and the object. Moreover, the electronic device may determine a range between the electronic device and the object based at least in part on the wireless-return signal. When the range between the electronic device and the object is less than a threshold value, the electronic device may determine: whether the range between the electronic device and the object is varying and/or whether to perform the predefined action.