I intend to add this feature to johnny5 as well, but as sirp said, I have to wait until I actually get a led whiz

Mine will be the most accurate as instead of just counting the number of buttons, each label in j5 will be binded to a led (just like the labels are now binded to a physical keyboard key) so remappings and re-arangments of the buttons on your panel for a particular game will be reflected.
Of course j5 is a tad slow to render a layout, so this would only be useful after a game is loaded, not while scrolling through a gamelist.