Typing with your hands is so retro.
There are no public APIs for using the Siri voice-activated assistant for dictation, so developer Avatron found a way to control Siri and convert speech into text. The text then transfers to the corresponding Mac (with OS X 10.6.8 or higher) running the Air Dictate Receiver app.
This means you can turn your phone into a speech recognition microphone and input text into Mail, Word, Pages, and whatever other app loves text.
While many speech-recognition programs exist for Mac computers, I suppose it is somewhat splendid to use a phone instead of a conventional microphone or headset. Would you really use your phone to type often, though?