Showing end of buffer

[Richard Stallman]

Dan Jacobson suggested

    Well, it turns out that if you add a special mark for the beginning of
    the file in the very left margin, then one does not anymore need to
    rely on "Top" in the modeline to tell us we are on top.

What would people think of displaying a special kind of horizontal
line reaching across the width of the window, to indicate the
beginning and end of the buffer?