Anyone that has children may find the Link Child Locator bracelets by Continuum Studio interesting. Both the parent and child wear one of the bracelets, and the parent bracelet lets you know the direction and distance to the child location. An alarm can be set to alert you if the bracelets separate too far, and the units have a 100' range.
The units are designed to be nested together when not in use, and each bracelet has a unique ID to ensure that digital connections remain specific to a given pair.
There are other locator units on the market, but these are perhaps the most stylish versions I have seen. In the design, the LCD display is integrated into the body of the watch, and the information is presented in a precise, informational way that can be easily read in moments of panic. The bracelets are sure to help give a parent a better peace of mind, and child safety cannot be stressed enough.
However, I wonder if there is another proximity detector bracelet coming on the market, one designed for the child's uses. In this case both parent and child wear the bracelets, but the unit can be set to alarm in case the parent gets too close. Perfect for those times they should be doing homework instead of playing a video game.