US Patent 7218211 Vehicle-based vehicle occupant reminder using capacitive field-based sensor

Methods and apparatus are provided for providing an indication to a person external to a vehicle, of an occupant inside the vehicle. The method comprises determining whether an occupant is in a vehicle, based on a capacitance measured within the vehicle; sensing whether an ignition of the vehicle is in an off position; detecting whether a first door coupled to the vehicle has been opened and closed, if the vehicle ignition is in an off position; if the first door has been opened and closed and an occupant is sensed in the vehicle, measuring a first time (T1) beginning from the instant the first door is closed; and activating the alert, if T1 is greater than a predetermined threshold time.