Here's an interesting twist on the urine story.

As you say bears can smell very well. So they smell more than just the fact that the urine comes from a human. Apparently they can tell if you are male or female. Female urine doesn't work apparently. This is the story going around my neck of the woods anyway.

I'm not sure there is any research on it. The original research comes from wolves. But them wolves mark their territory with urine. If they smell male urine they take that to be a territorial boundary (regardless of whether it's human or wolf urine) and pretty much respect that boundary. Female urine, of any species, doesn't phase them.

I'm a bit doubtful whether bears work on the same principle. But hey, urine's cheap right?