well the playstation controllers are not just shift register driven, like most older pads (atari excluded) they use a fairly pita serial protocall

course in this day and age it would be nothing to get an arduino, which already has playstation controller code and pipe it out to something the apple // could understand (or nes or sega)

If i were not already in a long and involved process with my arduino I would play with it, but if there is still interest in a month (when my deadline is up for the current project) I would be more than glad to whip up a board