iMessage is the Mac app (OSX and iOS) that can be used for a variety of purposes including sending text messages. One of the main advantages of using it is that text messages are free when using a wifi network. Using it on the Mac gets another advantage of the keyboard without having to pair one with your iPhone/iPad. Dictation has also been added to OSX and once it is enabled (settings, System, Dictation & Speech) all you have to do to use it is hit the 'fn' button (bottom left on the Apple bluetooth keyboard) twice, a popup should appear and you should be able to speak your message and then hit the function key one more time to finish it. I'm using it to dictate some of this post in fact and it works well enough to be convenient. A couple of links to useful info on iMessage follow: