I have heard it suggested that doctors carry medical waiver forms on them at all times. This is a bit sad really, as it is to protect them from being sued if they try to help someone in need. Personally, I think that there should be a law that if a person asks for help (or is unconscious and obviously needs help) that a doctor should be exempt from being sued, except maybe in cases of real negligence.
The idea that I might be within hands reach of a doctor when I or someone from my family is in trouble, and they might be having to weigh up the possibility of being sued before they help is scary.
On the other hand, asking people to sign a waiver when their life is possibly in danger would probably not work anyway, as it could seem like they were forced into it.
You just can't win.