Let the terminal bells ring out(muxup.com)

    function preexec() {
      lrn_timer=${timer:-$SECONDS}
      lrn_command="$1"
    }
    lrn_timer=0
    function precmd() {
      [[ -v lrn_timer ]] || return # preexec() doesn't set timer if no command run (e.g. from ^C before running)
      timer_show=$(($SECONDS - $lrn_timer))
      unset lrn_timer
      # 10 is the notification threshold in seconds
      if (( ${timer_show} > 10 )); then
        terminal-notifier -sound default -message "Exit $? in ${timer_show}s: $lrn_command"
      fi
    }