UPDATE: When asked about the "Okay, Google" feature, Google's Matt Cutts tells us, "I think that will take a little while longer, but Chrome updates move along quickly."
Update 2: While we should be able to expect the "hotwording" functionality in the future, a Google spokesperson only offered, "Conversational search has started rolling out on Google.com in the latest version of Chrome. You can just click the mic in the search box, ask your question in a natural way, and get spoken answers."
At Google I/O last week, Google announced that it was bringing conversational search to the desktop. Voice search features available to mobile users are coming to the desktop via Chrome.
You're supposed to be able to just talk to Google without clicking any buttons, and ask it questions, and otherwise perform searches. You've been able to use Voice Search from the desktop by clicking the microphone icon for some time, but now you shouldn't have to click.
Unfortunately, that functionality isn't quite available, but the Chrome update that is supposed to bring it to users has gone live, along with the makings of said functionality.
When you update to version 27.0.1453.93, you can click the microphone icon, and it will ask you if you want Google to start listening, so you shouldn't have to click any longer. The problem is that Google is not responding to queries after that, unless you click the mic icon as usual. It does at least speak answers back to you now. You can also continue the "conversation" in a natural way (at least on some queries), and Google will understand that you're still talking about the same subject.
Danny Sullivan uses the example of asking, "How tall is Barack Obama?" then asking, "How tall is he?" Google delivers without missing a step. It understands that "he" is Barack Obama. But you still have to click the mic icon.
In the demo at Google I/O, Google illustrated that you would be able to say, "Okay, Google," and conduct your search from there (not unlike the famous "Okay, Glass" command).
Right now, Google may be listening to what you're saying, but it's not quite up to the Star Trek experience just yet.
In the demo, Google refers to the "Okay, Google" command as "hot wording". There does not appear to be a setting in Chrome to set a hot word.
The feature is also a bit buggy, as people are seeing "no internet connection" sometimes even when they have internet connections:
This is actually happening a lot.[via 9to5Google]