A method for a supervisor to monitor the proximity of multiple charges--typically children, with the steps of: the use of portable radio frequency transmitters, the use of a common portable radio frequency receiver, the use of audible alarm(s), and/or light(s) or light-emitting-diode(s), and/or vibrating mechanism(s), the use of a method of identification for each transmitter's radio frequency signal, the use of a method of notification in the event of a loss of reception of any transmitter's radio frequency signal, the use of cases or enclosures for containing and carrying or wearing the transmitter(s) and receiver(s), i.e. wrist bands, clip-on cases, cases with carrying straps, and the use of portable power sources, such as batteries and/or solar cells for energizing the transmitter(s), receiver(s), and alerting device(s).