Yes this is an old thread, but the problem has just gotten worse, especially since the value of our cars has risen.
Having spent a lot of time (months!) on the road in my 70 Dart GT in the last year, and plan to do so again this year. I have thought about this a lot. On the road I always stay at old style Motels (and even hotels if I can get a first floor room) where the rooms open to the outside of the building, rather than into an internal hallway. That way you have the car parked right in front of your bedroom door. I bought a bright red Club steering wheel lock. I try and park with either a car or an immovable object next to one side of the car, nose in. Then I crank the wheel all the way toward the side away from the car/object and lock the Club in place. This does 2 things: The Club is really obvious to a thief and is a pain in the *** for them to deal with, and if they try to pull the car away with a tow truck or a roll back the car swings into what ever is next to you and gets stuck. Better to lose a fender than the whole car! You can't get a dolly under it if it is pulled up tight to what is in front of you. All this gives you enough time to wake up, call 911 and pick up the baseball bat that you bring inside each night. God help the thief that tries to steal my car.