"what is keyclone
essentially, keyclone is a p2p, unicasting keyboard emulator.
keyclone links applications together...enabling you to hit 'F1' within one application, and having that key simultaneously sent to each of the other applications keyclone is managing. it will also send those same keys to any other keyclones you may have linked in, which in turn will distribute the keys to the applications they are managing. "
That was taken from The FAQ
http://www.solidice.com/keyclone/faq.html
And it was originally made for Shadowbane. It makes a virtual keyboard so when I press the 1 key it sends that keypress to all the instances of the game and what ever each character has for the 1 key they will do.