This is my note for buffer-local function

gistfile1.el

(defun foo ()
  (interactive)
  (message "this is a default message."))

(defadvice foo (around my-foo-wrapper)
  (if (not (and (boundp 'use-my-foo) 'use-my-foo))
      ad-do-it
    (message "this is a special message.")))
(ad-activate 'foo)

;; in special buffer
(set (make-local-variable 'use-my-foo) t)

http://masutaka.net/chalow/2011-11-05-1.html (Japanese version only)