Emacs provides this with Follow Mode:
http://www.gnu.org/software/emacs/manual/html_node/emacs/Fol...
http://www.gnu.org/software/emacs/manual/html_node/emacs/Fol...
Sometimes I have the same file open in 3 or 4 columns if I need to see what is happening in multiple parts of the code in front of me.