Eeeek! That is terrifying!
If you had an accident with them set up like that, as your pelvis flies forward, the belt would just slip to your neck and end up garroting you!
Although you are right, it would be easy to set up!
I was looking at those ebay ones, but I'm thinking this is probably an area I don't want to cheap out on.
Although the ebay ones say they are E rated.... are they? lol