Google has released an updated Google Search app for iOS with streaming voice search, with some other new features and improvements.
Google Search v2.5 for iOS Updates
Updated for the iPhone 5
Improved Voice Search
✓ Simply say what you want and get results without typing.
✓ Faster and significantly improved voice recognition with text streamed on the fly.
✓ Get answers spoken directly back to you with web results tailored to your questions.
✓ Want to see types of questions that work well? Visit http://google.com/support/mobile/?p=gsa_voice.