I recently bought a new trailer and was looking for a little more security while it's in storage. I settled on a Lonestar tracking TitianLTE 4g/5g GPS asset tracker. Installation is easy, just make sure you have the tracker in a place where it can get a good signal (do not put in a metal box, says the instructions). I installed mine along connected to the battery for the winch.
The service is subscription based, $149/year per tracker. the tracker has apps available for windows, Mac, android, and iOS. The software is nice, it gives you updated battery voltage so you can remotely track the status of charge.
So far so good.