notify-erc.el

(defvar notify-command (executable-find "terminal-notifier") "The path to terminal-notifier")

(defun notify (title message)
  "Shows a message through the Notification center system using
 `notify-command` as the program."
  (flet ((encfn (s) (encode-coding-string s (keyboard-coding-system))) )
    (let* ((process (start-process "notify" nil
                                   notify-command
                                   "-title" (encfn title)
                                   "-message" (encfn message))))))
  t)

(defun my-erc-hook (match-type nick message)
  "Shows a growl notification, when user's nick was mentioned. If the buffer is currently not visible, makes it sticky."
  (unless (posix-string-match "^\\** *Users on #" message)
    (notify
     (concat "ERC: name mentioned on: " (buffer-name (current-buffer)))
     message
     )))

(when (bound-and-true-p notify-command)
  (add-hook 'erc-text-matched-hook 'my-erc-hook))