There are a few speech to text apps for the iPhone so if Android versions dont exist yet, they will soon. Note that those apps generally work by recording the sound file, emailing it to a central server, and sending you back the speech-to-text output. The versions that I have used all appear to limit the sound recording to 30 seconds or a minute or so.
I am not sure it is techinically feasible to develop speech-to-text apps on a cellphone OS like Android. I could be wrong though - since android devices are getting more powerful and the underlying linux is a pretty efficient and robust OS.