This isn't a plug for Cloudhawk, I don't own shares or anything. I mentioned this in another thread but I'll go into a bit more detail here. Cloudhawk is a Canadian company but they work anywhere in North America, and I imagine there is probably a plethora of US companies that offer the exact same thing.
The device is about the size of a pack of cigarettes and has a lead with 2 wires coming out of it. There is no antenna or anything external. You can mount them in the vehicle buried in the dash, in the trunk, under the car, etc. They cost $99 per unit and it's $100 a year to monitor/subscribe in Canadian money so $75 a year or so USD. They draw minimal power, less than a cell phonr and only report when when they move. In the event of power loss you get a text or email of the event. They have an internal battery so they will keep on reporting for several weeks. I have them in my tractor, excavator, side by side, trucks, etc. If the unit was stolen and you hid it well it would be very hard to find. They must use more than just GPS as they work in underground parkades and buildings with tin roofs. They do however need cellular coverage to report in. If they leave coverage and then get coverage they do report where they were while out of coverage. You can set geofences, or to text you it moves outside a certain time window , etc. I believe you can also get a text if it detects rocking the vehicle.
You might not be able to stop the theft but odds are high you will know where it is.
This one is buried in the dash of my Freightliner on top of the heater box.
