Children Wristwatch

Children Wristwatch
Can someone please tell me the name of a tracking device I can get for my child?

I have been homeschooling my son for the last several years but now he wants to go to public school. We tried this two years ago and one day I went to pick him up early and the school officials couldn't find him. It turned out that he was at lunch, but thirty minutes of searching for him gave me a severe panick attack. I'm looking for something like a wristwatch that really looks like a wristwatch and not something for a small child. A keychain or something that can be sewn inside a shoe would also be nice. It can't be a cell phone because they aren't allowed at this school. I'd like something that comes with a monitor that will tell me his exact location even when he's inside the school building and I'm in the parking lot. It would also be nice if I could see where he is when I'm at home and he's at school. Any ideas will be appreciated.

http://www.brickhousesecurity.com/about-child-locators-gps-tracking.html
Check this.

Lovely Frog Style Children's Wrist Watch from Dinodirect.com