Air Dictate is an iPhone 4S app by Avatron that allows you to use Siri to dictate text to your Mac. To use, first you must visit avatron.com/i to install the Air Dictate Receiver app for you Mac. Then, over your shared Wi-Fi network, you can share your Siri dictation to any Mac application that accepts text!
I just tried this out, and all I can say is - epic win! (Inputed with Air Dictate.)