Been experimented with earlier by the device vendors in voice recognition software and IVRs and not been very successful.
Google Mobile App for iPhone now with Voice Search and My Location
Google Mobile Blog, November 17, 2008 The new Google Mobile App for iPhone makes it possible for you to do a Google web search using only your voice. Just hold the phone to your ear, wait for the beep, and say what you're looking for. That's it. Just talk. Once the App is on, you don't have to push any buttons to search. Check out the video below to watch engineer Mike LeBeau explain how this works.
After you speak your query, Google Mobile App will return search results formatted for your iPhone.
And if you're doing a local search, there's no need to specify where you are because Google Mobile App now has Search with My Location. Search for "movie showtimes" or "Mediterranean restaurant" and you'll automatically see results based on your current location. For this to work, Location Services must be enabled on your iPhone and you have to opt-in to let Google Mobile App use your location.
To get the latest Google Mobile App for iPhone or iPod touch, go to the App Store and look for "Google Mobile App." Note that the voice search feature is currently available only in U.S. English and for the iPhone.
Watch this video to see what Googlers from Chicago, London, New York, and Mountain View are searching for. Then consider sharing your most interesting voice search query by submitting a video response.