There are several variations of this for tractor trailers, although it is secondary in the reasons it was designed.
Probabably first in use is Qualcom, a messaging system that monitors and records pretty much everything a truck does including speed/rpm/location and the time it happened. It is satelite based and is used by most of this countries trucking industry.
Highway Master is about the same thing, except cellular based.
Trailer Trac is a non messaging system for pinpointing trailer location. It tells location, empty or loaded and last movements, what truck hooked up to it and when. Unlike the others, it only updates once a day and has battery backup that lasts for about a month.
We had a trailer involved in a rail accident (not mine!!) and the railroad sent it to a scrapyard near our terminal. We finally sent someone to identify it as it showed being in a strange place with no activity and no record of one of our trucks moving it there. After figuring out what had happened, some of the shop guys went over there with sawzalls and cut the front of the trailer out to recover the unit.
David from jax