Kid's tracking device

Friends, need you help in finding a good tracking device for kids. My nephew is 3yrs old, and my brother wants to buy a reasonably priced and good tracking device (watch type, normal pen drive type, etc.) that he can keep with my nephew at all time (especially when he is on transit to school and back in Van service). I was searching on amazon and find variety of options starting from 1.5k all the way to 9-10k. Does anyone have first hand experience of any good device that I can consider buying?