Google has released the "Ok Google" search functionality for any computer running the Chrome browser with a microphone and on the Google search page.
Users can install the Google Voice Search Hotword extension through the Chrome browser Web Store, where it will then ask for permission to use your microphone from there on. After that you simply say “Ok Google” and then ask your question when using the search engine; it doesn't work on other websites.
"Ok Google" functionality was first released on Motorola's late-2013 line of Droids and the Moto X, until expanding further into all Android 4.4 devices in late-October including the Nexus 5.
The new Chrome extension doesn't feature as many functions as the Android including conversational search.
In practice, we found the new feature to be a bit finicky. You have to really speak up, and it had trouble even getting a basic search like "Pocket-lint" correct - it delivered "Oakland" to start with.
Nonetheless, it is a beta product so we do expect a bit of improvement on Google's end, over time, but it certainly starts you getting used to a world where you speak your searches rather than type them.