I think what he is trying to say is that it could just emulate the terminal and read whatever is coming to it after it's executed. "Listening" for when the user types in sudo...
The easier way would likely be to add a "sudo" script somewhere in $PATH, ideally before /usr/bin – incidentally, this gets much easier on a development machine where people have a ruby path, a perl path, a python path and their own $HOME/bin.
