I'm not 100% sure what the real uses for this would be, but a nice generic solution would be a program with 2 "regions", or rather a window and a region selector. The window could be placed and sized as desired, and would display the contents of the selected region, which could be moved anywhere.
So basically this is like a "magnification" tool, except that it can before enlargement or reduction, and doesn't follow the cursor, but rather shows the content of a selected region on your screens.
I wouldn't be surprised if such a program didn't already exist.. if someone finds it (or writes it!) please post.
Could be useful for given presentation talks, etc.