A system is described herein that comprises a communications device periodically transmitting a radio frequency signal, wherein the periodically transmitted signal includes data. The system includes a receiver detecting the periodically transmitted signal, the detecting including measuring strength of the periodically transmitted signal, the detecting including using the signal strength to provide a first estimate of the receiver's distance from the communications device. The system includes the communications device comprising at least one location sensor for determining an additional distance indication, wherein the data includes the additional distance indication. The system includes the receiver performing a function when the first estimate meets at least one criterion and when the additional distance indication indicates a first state.
