The sad reality is, anything done to stop a thief can be defeated giving enough time.
Other than the pager signaling me, I don't know a sure way to thwart a tow truck.
I'm aware of turning the wheels and locking the steering wheel, which can be cut off, or with with dollies or a flat bed, say goodbye. Yes, I have a tracker, if they don't know about it and defeat it.
Anyone have any thought on that?