Two Headed Penguins?

dmendesf asks: "The Octane2 workstation from SGI has a neat trick called PowerDuo that enables a single station to be driven by 2 keyboards, 2 mice and 2 monitors. Is it possible to do the same with Linux and USB mice, keyboards plus Dual Head videoboards?" How difficult would it be to develop an X11 solution to do this? Now take this a step further: could this be done with the secondary machine a network connection away?