So I was thinking. Some people have suggested some sort of sounds for animals and such so you can hear them. but sound effects are a pain in the ass, and while I do like sounds, and think H&H could use more sounds, I think this idea would be a good way to start before that.
You cannot hear, what you don't listen to. a simple toggle able or single use command in the adventure menu, the toggled version would have a short radius and work while you are moving, the single use would have a wide range and would take a second (the hourglass) of not moving to use. while the listen thing is in use, a little message pops up when you get close to something or something gets close to you. for example, you come up to a boar but you cant see it, a message would pop up in red at the bottom that says; you hear a rooting and snuffing sound nearby. with other players, you use listen. the other players stealth skill comes into play, if they are moving then you get messages like; you hear footsteps nearby. if the player is standing still, it gets harder to hear them. if you detect them, you get a message that says; you hear nothing, but you feel as though you are being watched. if they are in a boat you will almost always get; you hear the sound of water splashing on wood, if they are in the water without a boat; you hear someone splashing about nearby.
the other version, the one use one, would have a wider area of effect, but would give more varied messages depending on how far what your listening to. also instead of in red at the bottom, a message in a little window would appear for every different thing in your listening radius. so for example, you listen for a moment;
you hear the call of deer in the distance, you hear grunting nearby, something big is roaring in the distance, you hear someone splashing about not too far off.
The defualts would be stuff like; you hear the birds in the tree's or you hear water lapping on the shore, or you hear the drip of water somewhere off in the darkness.
I think this would also make stealth a bit useful, especially if some sort of "you cant see me, i'm hiding in the open" kind of stealth ever gets made.