The interesting part in Apple's FileVault (plus UEFI password) is a Guest access called Safari Only Mode. This mode starts special macOS distro from unencrypted boot partition and allows to run only Safari.app (also terminal.app) The main idea is that thief log in as Guest, connects to WiFi and you can locate your device in Find My Mac. But this mode just allows you to trace device via IP geolocation since macbook never had GPS module like iphones do, so this geolocation is not accurate enough and not useful. You will just see the city or district located from ISP. The real useful information will be WiFi AP MAC addresses (BSSID) located nearby the stollen macbook. Having this information you can quite accurate locate your stolen device and return it!

But I can't add my custom shell script into Safari Mode because of macOS SIP (system integrity protection) that I don't want to disable. Also every major update overwrites changes on boot partition.

I would appreciate for any help with this project. My goal is to build some kind of computrace for macbooks that will be much useful that current Find My Mac.