Vehicle security for long road trip

I have GPS tracking on a couple vehicles... Over last summer one of those vehicles was transported from Texas to California in an enclosed trailer, I was able to see every stop, fuel/food/pee/sleep.. I was able the see the speed the vehicle travelled, the altitude... I had heard there would be gaps in coverage.. There were none... I had heard GPS tracking doesn't work when the vehicle is inside a metal building... I saw it while in the metal trailer, I see it in my metal building... If you lean on the fender/open a door/ the hood/the trunk I get a message on my phone withing 15 seconds... The units I'm using are Optimus MV50's, When I bought them they were $50.. A few days ago the price had dropped to $40... The service is $12 a month... Hook up is two wires, power & ground... Setting up the app is super easy...