The Voice Search enhancement is expected to be available soon for both iPhone and iPad running iOS 4.2 or higher. Voice Search for iOS combines Google's existing speech recognition with the ability to interpret natural language for a more comfortable search experience.
Since the Voice Search update understands “natural language” you can ask questions like “What will the weather be like tomorrow?” and your question will be answered by human-like voice. Not only that, your words are streamed back to you as you speak, letting you know that your voice is being recognized.
According to a blog post by Amit Singhal, the accuracy of Voice Search is possible thanks to the Knowledge Graph. The Knowledge Graph is a database of “more than 500 million real-world people, places and things with 3.5 billion attributes and connections among them.” Google uses this information to find results for your questions quickly and accurately.
Check out the promo video for the new updated Voice Search app coming to iOS 4.2 and above.