An electronic device for detecting the presence of an occupant on board a vehicle includes an audio sensor to acquire sound-sensing signals on board the vehicle. A movement sensor acquires movement-sensing signals associated with movement of the vehicle and an environmental sensor acquires environmental-sensing signals on board the vehicle. A processing unit is coupled to the audio sensor, movement sensor, and environmental sensor processes the respective sound-sensing signals, movement-sensing signals, and environmental-sensing signals to monitor the presence on board the vehicle of the occupant and the absence of a responsible person to determine a situation of danger and to activate a corresponding alarm warning.