This is a cool little minor mode hack for Emacs. It’s like a last-typed heat map.
Onlookers will be amazed as you burn up the screen with your brilliant code.
Update: Rafal Jedruszek’s site above has gone AWOL, so I am preserving a copy here:
Highlight Tail (1984 downloads) version 1.3.9 (02 Apr 2007).