My friend had the same problem so she got her son an autism dog that he is attached to and she has no more problems with that becouse the dog stops him. her son takes the dog to school, shopping ect. everywere he goes his last time he ran off he almost got hit by a car and she had enough so she got the autism dog and that made a major help and she no longer had to worrie about him taking off becouse the dog was always attached to him good luck here one of the sites i was looking at for my son

autismservicedogsofamerica.com/

You might want to enter "wandering" in the search above - this question has been asked several times - also questions on trackers, etc.
I got the following from an article on the Internet about a lost girl with autism (seem to be so many cases these days):
The tragic phenomenon goes by various names — wandering, elopement, bolting — and about half of autistic children are prone to it, according to research published last year in the journal Pediatrics.

My son used to do the same thing. I know it sounds weird but I bought a kids safety leash.

We've dealt with wandering for years. The police actually know us :( Autism Speaks has some good resources. http://www.autismspeaks.org/wandering-resources

yes except the IONKIDS tag is only good up to 350 feet outdoors