Jott converts your voice into emails, text messages, reminders, lists, and
appointments 

Jott turns your voice into emails & text messages. Simply call Jott and speak
your message. Jott converts your voice to text and sends your message. Jott
can also create reminders, lists & appointments. 

Jott makes it simple to record your voice with a couple of taps. You can then
categorize those recordings into groups, and easily mark them as completed
with a swipe of your finger. What wasn't apparent to me, though, is that Jott
on the iPhone is tightly coupled to the Jott Web service - you'll need a free
Jott account to use the program. After speaking into your iPhone to create a
note, the note is sent to Jott's server, where the audio is converted to
text, then synched back to your iPhone. In my testing, this worked accurately
and well, though sometimes my iPhone displayed only a "waiting on
transcription" message, and sometimes I saw that message twice for a
recording I made only once. A planned update promises to address these bugs.  

Beyond the Jott application, you can use Jott's toll-free number to speak
tasks you'd like to have done, including things like searching Amazon with
results sent to your e-mail account); creating blog entries on various
services; sending a message to Twitter; sending reminders to yourself; and
much more. Jott converts your voice to text and then uses that text with the
service you specified. 

Jott:
http://jott.com/Default.aspx

Obviously Jott could be used to communicate to people who are hard of hearing.