Best of all, you could wear it yourself.
The video above walks you through the project.
At the core of the setup is the sewable, Arduino-compatibleAdafruit FLORAand its GPS module.
Granted, the system isn’t useful for finding a lost pet or tracking your pet in real time.
You have to have physical access to the harness so you can download GPS data.
Hit the link below for the full walkthrough and parts list.
GPS Logging Dog Harness| Adafruit Learning System