This is what the Clifford allows with BlackJax. If they take your car keys and immobiliser fob, they can start the car as normal and it will allow them to get a certain distance away while monitoring the revs. It will warn that something is going to happen and you have to enter a simple code in the 2 button panel switch within a set period. If you don’t, the car cuts out and sounds the alarm. Can’t restart it without the code.
As stated above, it stops would be determined thieves, from ransacking the place looking for the keys and threatening you and your family to hand them over. It will allow them to drive away a safe distance before immobilising the car. Also works the same in carjacking scenario; hence the name.
A ghost device merely stops the vehicle from starting. If they really wanted the car, and you were present, they could just threaten or force you, through whatever means, to enter the code. Again, that is the same in both scenarios listed above.