Any parent who has ever taken a small kid to a large zoo, amusement park, museum, or who just has a reason to fear their kid might make a mad dash or decide to play hide-and-seek in public, has worried about what would happen if you got separated from the child. Fear and stress can make grown-ups forget important phone numbers, sometimes a lost child has trouble with their own name.
Now imagine your child has an allergy or other medical condition that causes worry. Perhaps your child is older but still non-verbal or is otherwise unable to communicate with strangers.
No matter what their age or abilities, we want our children to have the opportunity to fully experience the world. How to do that, and still keep them safe?