When I first heard of the MS feature, my first thought was that there's gotta be a more efficient way to do this than taking screen shots and analyzing the image. The window manager has all of that information plus more context (like knowing that these pixels are part of a non-standard window that uses transparency to act like a non-rectangular shape, while this thing that looks like a window is actually an image because the user was looking at someone else's screenshot).

Even better would be integration with the applications themselves; they have even more contextual information than the window manager has.