a computing device incorporates a user sensor to signal when a user is moving or within a specified proximity of the computing device . if the user is not present , the computing device will go into a low - power mode . a real - time clock is programmed to interrupt at user indicted event times and dates . if a queued event occurs , the computing device samples the user sensor and begins notification procedures if the user is present . if a queued event time occurs while the user is not present , then the computing device enters or stays in the low - power mode . if the user sensor indicates that the user is present , the computing device notifies the user of the pending event and any missed events . the computing device may require a user code before normal operation is activated following a transition to an indication that the user is present .