Project Lifesaver is a nonprofit organization that provides families with mentally disabled individuals, a bracelet that connects to 1st responders via radio frequency. Project Lifesaver has such a high success rate, they have partnered with police and 1st responders in all 50 states! (https://projectlifesaver.org/)
These types of devices (of course) only work if you use them consistently and have them setup BEFORE the individual runs away or becomes lost. If you have not contacted your local emergency management office and discussed the services available to you as an autism family, please do so soon! We would hate to image what could have happen to the young autistic boy in this video, without his Project Lifesaver bracelet.
AngelSense is a similar product that works via GPS. AngelSense provides a variety of wearable devices that locks around the persons body or clothing and can only become unlocked with a key held by the parent or guardian. (https://www.angelsense.com/)
We hope this information helps you prepare for the worst...and we hope the worst NEVER happens.
Love and Kindness,