Hi GGS,
Are you looking to have simple commands processed or have it recognize ANY text spoken? These are two very different problems to solve.
FYI - There are
text to speech libraries available on iPhone and Android actually has it built into the OS starting at version 1.6. However, this doesn't help you. :)
What you are asking for is
speech to text translation. I've been doing work in VoIP for a few years now and have found some server side telephony services that do this. There are some "free" services and others that cost a lot of money. As with most things, you get what you pay for.
http://www.spinvox.com/http://www.lumenvox.com/http://www.twilio.com/docs/demos/voicemailtranscribe
http://www.ribbit.com/mobile/tour/voicemail_transcriptions.php
It's a pretty cpu intensive intense process to do anything more than straight voice commands (i.e. "Call Mom", "Call Home", etc..) directly on the device. Can you imagine the vocabulary and dialects that would be needed for the entire English language? I haven't looked around much for these app, but what I'm guessing you will find are services that are "apps", but they do all of the heavy lifting server side.
For example:
http://www.voip-news.com/feature/promptu-iphone-app-030309/There might be some apps coming out that do it right on the phone, but none that I know of. So, a round about way to answer your question.
a) Has anyone done a comparison of voice transcription/recognition
capabilities of Android and iPhones?
There isn't really any difference, because the work is done by the speech recognition software on the server. If you have good recognition (or have call centers overseas to do your transcription :), you'll have good results.
b) How easy is it to code this feature for iPhone and Android?
It's would be a matter of making calls into whatever service you want to use. The platform shouldn't really matter. In fact, speech to text can easily be done on any phone. It doesn't even have to be a a smartphone. Your old Nokia will work just fine as it's your voice being sent to the server, processed and then returned.
Justin