I too have been looking at locks and came across this today.
This looks fairly secure and well made and they have an Airstream version. http://provenlocks.com/products/mode...tream-couplers
They have a video showing other locks being defeated. However, on a few, I noticed he locks the coupler and then at the beginning of the next sequence when he is defeating the locks, the coupler is in the open position. On another, you can tell he had a pre-video, head start with a smaller pry bar and sledge. That's not to say these locks couldn't be defeated without these "cheats", it's just not a straight forward comparison.