[alxfrnr]

For a total opposite tool, there is mousemux (Windows only). You can get multiple mice on the same machine and you can attach a keyboard to each and lock it to a window or a screen.

[sneurlax]

Whoa! Now that's interesting! I wonder if that would be possible on other OSes...

[salmonik]

It can be done on Linux with X11 using xinput.