I noticed you said grappling hooks and the like are not worth your time. But check this out:
http://www.botacht...al.com/cagrho.html its made out of steel which is great because the failure point of steel will only occur at that specific load. They do have an aluminum one but stress is cumulative on aluminum so it could possibly break one day without much force at all. At any rate I plan to pick up one of these bad boys in the future. When I perceive the need.