The Kiddo device certainly takes a more humanitarian approach when compared to those ‘kid leashes’. You know, the ones you see parents tugging on at the mall? It can monitor kids, or those with a tendency to get lost or go missing, in two distances: 4 meters and 8 meters. If the child wanders beyond the parent receivers preset proximity an alarm will sound and a light will blink. To insure that a perpetrator doesn’t disarm the child’s device, Kiddo requires the units be placed directly on top of one and other for activation and deactivation. Runs on a two AAA batteries. It’s available, but probably tough to find here in the US since it’s built in Portugal.
Product demo here (warning: PDF)
More info here.
More pics after the ‘leap’