Trackers are useful but not going to stop the experts. As said above, they are not good at communicating through steel, so anything in a container will be difficult to track. As well as the subscription monitored units, you can get relatively cheap battery powered ones with a sim, where you put an App on your device to track it. Obviously they need a good phone signal to transmit, which can be an issue in some places.
Yes, Tracker’s in or on trailers a good idea, as long as they’re well hidden. You can even get them for bicycles nowadays....
