Run, run as fast as you can...

Diego decided to walk to school today. Understand that school is not close to our home, therefore it is not within walking distance that's why I drive him to school. Thankfully Diego used the overhead garage door to leave the house and I heard the sound of the door (something I've complained about being too loud since we had it installed). When I got outside there was no sign of Diego on the sidewalk or in yards close by.
I took off in my car, cell phone in hand to begin the search. I frantically called Joe, voicemail. I then called "Aunt Za-Za" who works nearby, she would come from the opposite direction and search our school route while I drove the neighborhood scouring bus stops. I then had to call the police who began to search as well.
20 minutes into the ordeal Za-Za called and said she had him. He was quite a distance from the house and really didn't want to get into her van but she was able to convince him he needed a ride. (There was a slight incident where a kind woman may have believed Za-Za to be a child abductor.)
A very nice police officer arrived shortly to talk to Diego about not walking away from home or school. She explained how important it is to be safe and that walking that far to school is not a safe thing to do. She made him promise not to walk away again. An uneventful day at school ensued.
Well, believe it or not when I arrived after school to pick Diego up from the latchkey program, I was met by a little girl who told me Diego wasn't there, he had run away. She was followed by an extremely distraught childcare worker. It seemed Diego had become upset and ran into the building locking the group outside. He grabbed his backpack and ran through the building to the front exit door.
I began to search around outside the building after a quick check inside. No sign of Diego. I met the principal and a teacher who had been searching the neighborhood. There was a football game and a soccer game going on in the area too!
The police were already looking for Diego. A patrol car pulled up in front of the school and the officer inside said another officer had found Diego at the Tim Horton's... a very long way from school and a dangerous route for him to travel on foot.
Soon the other patrol car pulled up with Diego in the front seat clutching his backpack, no worse for the wear.
He acted as though walking home shouldn't be an issue for me or the others looking for him and told his principal he really wasn't afraid to be that far away from school by himself.
I'm considering the purchase of a child monitoring system but the only ones I've found will work just 500' from the base and he would have to wear the 'indestructible' wristband at all times. There is a GPS available but it can take quite a long time (up to 20 minutes) to alert the base of a problem. Anybody have a suggestion for monitoring the boy? I'd love to hear it.