#+Title: Periodically Rerun a Code Block

Here's the lisp code to define a function to continually re-run a code
block.  Evaluate the following code block, then =M-x continually-run=,
press ENTER and then type in the name of the code block to continually
run (in this case "date").
#+begin_src emacs-lisp :results silent
  (defvar continual-runners nil
    "Holds running block timers (so they may be canceled).")
  
  (defun run-block-in-buffer (name buffer)
    (save-match-data
      (with-current-buffer buffer
        (save-excursion
          (org-babel-goto-named-src-block name)
          (with-local-quit
            (undo-boundary)
            (with-temp-message (format "re-running %s" name)
              (org-babel-execute-src-block))
            (undo-boundary))))))
  
  (defun continually-run (name)
    "Continually run the supplied code block name.
  The code block is assumed to be in the current buffer."
    (interactive "scode block to continually run: ")
    (let ((run-buffer (current-buffer)))
      (add-to-list 'continual-runners
                   (run-at-time nil 5 'run-block-in-buffer name run-buffer))))
#+end_src

Here's the code block to be continually re-run.
#+Name: date
#+begin_src sh
  date
#+end_src

And here are the results which will be continually updated.
#+RESULTS: date
: Wed Jan  9 22:04:08 MST 2013

Execute the following to stop all continually updating code blocks.
#+begin_src emacs-lisp :results silent
  (mapc #'cancel-timer continual-runners)
#+end_src