Hardware :: Two Combinations Of Screen/input On One Machine?

i know it's possible to have different users with each a mouse, keyboard and screen work on one machine at the same time with different user accounts. My questions is, how can i make possible a setup where i have two distinct sets of physical i/o on my computer, but nevertheless work in the same X session with virtual desktops.For each set of input/output devices i would like to have an own activation (e.g. when i click on a window with mouse A, the window will be focused on screen A, but the focus on screen B must not change (unless i steal a window from B or both displays show the same virtual desktop))