I wrote a tool that does just this: https://github.com/timmmm/anakin

If you run `anakin <some command>` it will kill any orphan processes that <some command> makes.

However is still isn't the true "orphans of this process must automatically die" option that everyone writing job control software wants - if `anakin` itself somehow crashes then the orphans can live again.

Still it was the best I could come up with that didn't need root.