Doesn't the Apple Magic Mouse include that functionality? I believe if you just swipe left or right with one finger, it mimics the effects of a dedicated button.
It sure does, but the swiping only works with the "magic mouse". The "mighty mouse" has a ball in the center and two side buttons. They together act as a back button and the center ball can be clicked to perform some other action.
Anyway, I have each of these (which I never use), and I could detect these extra key presses, so it's "only" a matter of implementation to support it in jAlbum