Wind the clock back two years with your smart phone in hand. Try to recall doing a search for a restaurant or the latest scores of your favorite sports team. If you’re like me you probably won’t even bother, or you’ll suffer with tiny keys or fat fingers on a touch screen. With Google Search by Voice all that has changed. Now you just tap the microphone, speak, and within seconds you see the result. No more fat fingers. Google Search by Voice is a result of many years of investment in speech at Google. We started by building our own recognizer (aka GReco ) from the ground up. Our first foray in search by voice was doing local searches with GOOG-411. Then, in November 2008, we launched Google Search by Voice. Now you can search the entire Web using your voice.
Link to full case study: http://googleresearch.blogspot.com/2010/09/google-search-by-voice-case-study.html