child perimiter alarm

hi im looking to build a simple kit that i can put a small transmitter on my child and i keep the reciever.

when my baby leaves the perimeter 5 or 10 meters a alarm will sound.

any ideas where i can find such a kit or a diagramm

regards

k. varkel
kaz@plet.co.za
South Africa

I've explained a basic way of implementing this in the thread linked below.
https://www.electro-tech-online.com/threads/ideas-for-a-distrance-tracker-for-dog.26551/

Good idea in theory, but having something like that would encourage ignoring the child's known location trusting a piece of hardware, which may fail. If you have a small child that needs to be watched that closely use a wrist strap. Whole lot simpler and more reliable.