All that said, when Emacs and iPhone can both respond to a particular requirement with “there’s an [app|elisp package] for that,” the iPhone variation will usually involve a quick download and three or four fields in a configuration screen, tops.
Twitel is a Twitter client for Emacs. It was previously known as twitter.el. It's just a simple Emacs lisp script but it lets you view your friends timeline and edit a new one so it's quite quick if you're already running Emacs (what else would you be doing?).
To approach an IMAP mailserver from within Emacs, you need to install additional software in Emacs. Wanderlust is an proven solution to add IMAP capabilities to Emacs.
There are certain emacs commands that can be used in just about any generic text field in OS X. First I will list some commands and then I will explain where they can be used.