The Google search application for iPhone (and iPod Touch) was updated yesterday. Now you touch the icon to open up the application, hold it up to you ear like you were taking a call, and speak your search request.
I just tried it (with a topic du jour) United Auto Workers. In a few seconds (five) up pops the usual Google list of possible sites.
Recognition isn’t perfect, but it’s a start.
The Bits Blog has some info on why speech recognition is an important breakthrough technology for mobile device manufacturers (because the keyboards are so small and difficult to use).