An alarm system for use with a motor vehicle to sound an alert whenever child passengers are left unattended and belted in a parked motor vehicle, including a transmitter for generating a radio signal characterized by a predetermined frequency, a receiver for receiving and rectifying the radio signal, a sensor for sending an ignition status signal to the receiver if the vehicle ignition is on, a timer for sending an activation signal in response to the receiver receiving the radio message and the ignition status signal, and an alarm for generating an audible signal in response to receipt of the activation signal.