Comment 3 for bug 315932

See:
http://blog.dustinkirkland.com/2010/07/dear-command-line-please-ping-me-when.html

Developed independently from this bug...

  alias alert='notify-send -i gnome-terminal "[$?] $(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/;\s*alert$//'\'')"'
  sudo apt-get install libnotify-bin
  sleep 20; alert

The response in the comments from planet.ubuntu.com readers has been very positive. I think it might be a nice addition to Ubuntu's bashrc. It won't make things noisy, as Doko mentioned, since the user has to do "; alert" at the end of their command.