Google Now style voice search has just went live in the latest Chrome stable version for the desktop (Version 27.0.1453.93). As far as we can tell from
playing aroundtesting things, the full contextual search isn't running like we saw in the demo during the Google I/O keynote, but the basic voice search and response is ready to go.
Announced and demoed at I/O last week, Voice Search for the desktop mimics the experience launched on Google's Search app for iOS last year. Voice Search for the desktop lets you dictate search queries to Google, which will transcribe them in (almost) real-time and take you directly to results, powered by the Knowledge Graph. Like on iOS, certain queries will trigger a voice response by Google itself, whereas others will display cards of information or regular results.
It appears Google is rolling out the feature this morning, as the new voice interface is available in Chrome but leading to frequent "No Internet connection" dialogs; I was able to try Voice Search twice, and it worked as expected.