So as can be guessed by the title, GameGear gear-to-gear cable emulation has been added to RetroCopy for the next version.
Thanks to RetroCopy's modular design it didn't take long to add it either. There are still a few bugs in some games but for the games it does work on it works well. In the input config section there is now a place to specify a player 2 for the GameGear controls. Simply assign some controls, select your game and you're away.
You're probably going to need a ~2GHz dual core to play it as it requires emulating two GameGears at once, both at cycle accuracy, for that extra little push over the cliff.