Similar to the 1-hour app that lets you drag a window without activating it and bringing it to the top, this would allow you to interact with the GUI of an application without bringing it to the top.  For instance, if you were taking notes from a large graphical window, you could do so without having to switch back and forth between, say, notes and the large graphical window you are studying.  (And if it sounds like I have suffered through this exercise, that would be because I have.)