This may not meet your needs, but there is a tool that allows sharing windows (X- or MS) called VNC. One scenario would be to have your tool run in a window (again, X- or MS) and share just that window using VNC (it can be password protected). All users' input is sent to the window and all output would go to all users. You can configure it to only share output with just one user doing the mouse/kbd input. For sharing just one window, be sure to get the VNC server configured that way -- the standard one shares the whole desktop!

HTH, --traveler