Keep in mind that trackers won’t stop your car from being stolen, but they can help alert you to it being moved, and help find it. If they are wired up fully, they can also be used to remotely disable the vehicle. It’s sort of a second-line defence device. But every bit of security helps imho.
An AirTag is essentially a passive device (yes, it is sort of active as it does transmit a short range signal) and relies on being able to communicate with nearby Apple phones to report its location. But for it’s low cost, it’s definitely worthwhile considering.
Definitely consider some sort of tracking device, whether it be an AirTag or a proper GPS tracker. The cheaper devices (such as those sold by Jaycar) do work okay and are good value for money. They work well with a cheap SIM card (Aldi is usually recommended as they have a 12-month expiry between reloads). The web app provided with these cheap devices is a bit hit and miss but it does work. The redeeming feature is that these cheap GPS trackers work with SMS messages so you can simply send a SMS to the tracker and it‘ll respond accordingly. It’s a bit clunky but it does work. The trick is to do a practice send of the messages to the device so that your phone has a history of those messages. It’s easy to cut and paste (and resend) a message.
The GTKPro2 is a data-only device and it doesn’t work with SMS messages at all. However, it does seem to have excellent support, an excellent website and an app that works well.
In general, I do think it’s important to think about car security, and to implement unique solutions. For example, if we all secured our cars in an identical manner, then the thieves will also soon learn how to defeat our theft prevention measures. So definitively do your own unique approach and try and be as innovative and individual as possible - avoid cookie-cutter approaches . The deeper you can bury your security devices, the longer it will (hopefully) take the the thief to defeat it.
I’ll place this thought out there for your consideration using an example of a simple kill-switch… if the thief finds the kill switch, it is easily defeated - flick a switch and steal the vehicle as usual. But if that kill-switch was wired so that it shorts out something (and destroys something - such as a fuse or a module) then it complicates the process of defeating it as simply searching for (and finding) the switch won’t defeat the security measure. It might sound drastic, but I think it would it be better to have to buy a new part than totally lose a car to theft.
Also, make sure that your car is insured!