There's a thread somewhere here with numerous methods of accomplishing this task that I and others have tried. If you must have a phone number to call, Google Voice and voicemail may be your best bet
- set it up to recognize the number you'll be calling from
- send that number directly to voicemail
- configure it to email you the transcript of voicemails
- set up a Gmail filter to forward that to OF either by the new beta service or using some kind of email-to-text and AppleScript
If you don't need to be able to call a number and are on an iPhone, I highly recommend DropVox and AppleScript – won't give you the transcript of the dictation, but you'll get the message. Here's a post I wrote on it a while ago:
http://www.n8henrie.com/2011/06/drop...and-omnifocus/
I've since updated that workflow to use a shell script to upload the transcript to CloudApp and insert the URL into an action, keep sync times quicker than having to sync the actual audio files.