Some nice ideas in here. Not sure if someone mentioned it yet, but having a manual transmission will stop a lot of people.
Since my car is fuel injected, I've thought of cutting off one off the tach signal to the EFI. That would let the car turn over, have spark and have fuel pressure, but the EFI wouldn't think the car is started and wouldn't let it run. So if someone was trying to hotwire it, it would be pretty far down the list of things to check. I was looking at adding a bluetooth relay to cut off that signal that looks like it could belong there.
Something like this (but all black) stashed in with other wiring and cut off that signal
https://triggercontroller.com/product/trigger-one-bluetooth-relay/. It would also be pretty easy to bypass should it start acting up.
On tracking, I've had this in my car for a few years
https://www.amazon.com/gp/product/B07PWLQLW5/. It was about $20 when I bought it and there are lots of new versions and different variations of it. It's definitely not elegant as you provide your own SIM card, all the setup is via SMS commands and the online tracking part isn't beautiful, but it's very accurate and has always worked for $5 a month. I've seen these kinds of trackers now in smaller form factors and some that look like a standard 12V relay like that bluetooth module I linked to above so could be hidden in plain sight under the dash or under the hood.
Then while not as accurate, there's things like Apple and Samsung tags that can be hidden just about anywhere on the car as a very low buck last resort tracker.