Is there any ability to redisplay, duplicate, a fraction of the video from another screen as an overlay?

After seeing the feature popup in hotkeynet's changes I tried to write a always on top vnc viewer that just shows me a specific geometry xy,xy to bring the minimap from my second display to my first display. Works pretty poorly, i think because vnc is actually grabbing my whole display screen and thats a little on the big size.

The possibility of using a custome viewport and making the minimap not 'appear' on the slave screen is appealing. But just have it tucked away under the left side of the windows or off the screen, but displayed on the main's screen just fine. Something like this for a dual screen setup on the slace side (red being the physical monitor and the overlapped or off screen areas with the minimap are not visible...