A processor-based personal electronic device (such as a smartphone) is programmed to automatically respond to data sent by various sensors from which the user's activity may be inferred. When one or more alarms on the device are temporarily disabled or ignored, they may be automatically restored when sensor data indicates a change in the user's activity. The restoration of alarm functionality may be accompanied by a repeat of notifications missed or not responded to during a certain period prior to the sensed change in user activity.