BTW even the old version of Dragon, i.e Dragon Dictate 3.0 can transcribe audio files. You can record audio on your iPhone, then transfer these .m4a or .wav files to your Mac for transcription. Error rates are higher when compared to dictation, and there's no interactive interface to finetune the transcription accuracy. I think the new version, Dragon Dictate 4.0, comes with better out-of-the-box transcription accuracy and/or better controls.
A regular audio out cable, such as the one that connects your iPhone to external speakers, can be used to connect to the audio in port of your Mac. Not sure if this gives good quality though. Dragon Dictate is incredibly sensitive to quality of microphone input unlike inbuilt Mavericks dictation, so try out the audio-in trick with inbuilt dictation first.
The recommended way is to install the Dragon Remote app on your iPhone, put both Mac and iPhone on the same wifi network, set up the iPhone as a remote microphone for Dragon Dictate, and thereafter work with Dragon Dictate dictation as usual.