The basics of what I'm after is very, very simple: Push a button, it notes your location. When you reach that point again it tells you. I've looked around and I don't find anything that seems to meet this description.
Use case: Yesterday on the way out I noted two pieces of trash. I generally pick up trash on the trail but not with that far and hard to go (3000' climb, 9 miles, many snow patches.) Of course I didn't see them on the way back down.