The only problem with attaching a PLB to your child is that they need to be activated/deployed to work. I don't think (and correct me if I'm wrong) they can be "pinged" but need to be activated by the user. My knowledge may be dated but I think you need to pull out a big antenna, too. A small child may or may not be able to understand how to use one. [Note: Some folks with kids tell me their 2 year olds can figure out how to use every function on a remote control, so maybe I'm not giving the little ones enough credit.]
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman