On some e200(and Fuze) plugin keymaps, the scrollwheel is used for up/down with the left/right buttons used for left/right when moving on grids. Not sure about iPod yet, but if it is the same there, this applies.
Plugins I know of include:
Superdom
mazezam
sudoku
Some plugins use the up/down buttons to do the up/down bit. The rest should follow that pattern right?