Dino, the first question you need to answer is, IF your caravan is stolen, trashed and made into a total wreck , do you really want to see it again?
Secondly, if it stolen and the tracker works, and the Police actually manage to find it, maybe badly damaged during it forced removal, do you really want to see it back?
If you can honestly say Yes you do, then that is the time to consider trackers.
The choice is vast, but you only get what you pay for, and the responses so far on how reliable they are is not particularly encouraging for any make.