Add native MacOS notifications to Emacs...simply.

init-terminal-notifier.el

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;; Terminal notifier 
;; requires 'sudo port install terminal-notifier'
;; stolen from erc-notifier
;;
;; (terminal-notifier-notify "Emacs notification"
;;                           "Something amusing happened")

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

(defun terminal-notifier-notify (title message)
  "Show a message with `terminal-notifier-command`."
  (start-process "terminal-notifier"
                 "*terminal-notifier*"
                 terminal-notifier-command
                 "-title" title
                 "-message" message
                 "-activate" "org.gnu.Emacs"
                 "-sender" "org.gnu.Emacs"))

(defun timed-notification (time msg)
  (interactive
   "sNotification when (e.g: 2 minutes, 60 seconds, 3 days): \nsMessage: ")
  (run-at-time time
               nil
               (lambda (msg) (terminal-notifier-notify "Emacs" msg))
               msg))