GPS trackers

Hi all, 

I am new here so please excuse me if this has been done before. I've been searching high and low for a reliable gps tracker for my son. I've spent quite a few pounds on various things and nothing does the job. loca8t, my buddy, the little teddy thing. I've bought gps trackers that turn out to be American or eastern made and aren't suitable for the UK. The apps don't always work in UK or the one I'm using right now bleeps on my phone constantly and doesn't give accurate information. 

My son is 9 years old, has no speech, no sense of fear and he is a high flight risk to say the least. Does anyone use anything that actually works and alerts you if child has gone out of range (Other than the ones I mentioned above)? 

Thanks for reading.