Look into a service dog. They help prevent wandering. They also alert caregivers of impending seizures and self harming behaviors. They provide deep pressure and will get a kid to exit the building for a smoke alarm.

Here is one you wear in your pocket
http://www.amazon.com/PocketFinder-Outdoor-Pers...(Phone number can only be seen by the question and answer creators)[bbc|LESPRIX

I have heard good things about this tracking device.

https://www.angelsense.com/product-tour/

I've been using angel sense for a week. ollie doesn't really like it attached to his clothes. he's been telling people its his phone. i told him its an exercise tracker. I'm thinking of trying the belt with it. might be less noticable plus my hubby wears one when he rides- be just like dad! some uncomfortable questions from preschool though about the listening in aspect. ah well too bad. OT S safety is paramount.
Id love to get ollie a service dog ;-)

i was looking at angel sense the other day. it looks good - i'd just need to remember to put it on him!