Interface with games consoles/creating controllers

Hi all, just quick question that must have been covered before (although I'm struggling to find anything):

Are there any examples/libraries out there for using the Arduino as a controller for older consoles? I'm well aware of the various libraries for decoding PSX, N64, NES etc. controllers as an INPUT to the Arduino, but can't find anything in the way of OUTPUTting those messages to connect to the consoles.

I've also seen UnoJoy (and its affiliated projects) but really I'm after controlling older consoles.

If libraries exist to decode the messages sent out by the controllers, surely it can't be too difficult to send them back out. I'd love to create my own controllers, or even try sticking an Xbee between an original controller and the controller port to create wireless versions of original controllers.

Any advice/previous threads appreciated!

Cheers.