Good idea. I find a rectangular mirror gives you the big picture. Listen and look back ofter.. I for one always loudly say, passing on left.. One problem I have experienced on bike paths, the person you are passing are not listening.. Or maybe they have a radio with earphones on. They are impossible.. Another problem, walkers/ joggers off the path entering the path and don't look.
They did not indicate their intentions but quickly walked out into my pathway. I have had to swerve for a couple of them or we both would have been hurt.. Some time pedesterians are just know to walk out in front of cars and don't look first..
Another problem I sensed today.. The Oceanside bike path is elevated above a river plain.. Today, I really sensed some one was out in the brush shooting. Not sure, but felt some object was projecting ahead of me. Thought I sensed a movement of air ahead of me... If this actually happened, I suspected it might have been like a bb gun.. Hope my senses were way off base.. We have lots of weirdo's about..Maybe I should call the police. We do also have some homeless living in this flood plain..
If the case, just something more to worry about..