Simple command line invoked timer. I plan to add some way of notifying.

timer.lisp

#!/usr/bin/sbcl --script

;;; Documentation:

;;; Commentary:

;;; Code:

(defun timer-tick ()
  "Waits for 1 second"
  (sleep 1))

(defun update-display (time-left)
  "Write TIME-LEFT to stdout, replacing whatever was on the last line previously."
  (format t "~C~D" #\return time-left)
  (finish-output))

(defun run-timer (time)
  "Runs a countdown timer for TIME seconds."
  (loop
     for current-time
     from time
     downto 1
     do (progn
          (update-display current-time)
          (timer-tick)))
  (format t "~CDone!" #\return))

(defun my-command-line ()
  "Reads command line args."
  (or 
   #+CLISP *args*
   #+SBCL *posix-argv*  
   #+LISPWORKS system:*line-arguments-list*
   #+CMU extensions:*command-line-words*
   nil))

;;; Script:

(let ((time (parse-integer (elt (my-command-line) 1))))
  (run-timer time))