Android 4.4 Kit Kat added some functionality for the ‘OK Google’ voice command. Basically, you can now use the command without having to tap the microphone icon. Of course, those using a Moto X have it sightly better thanks to Touchless Controls. But while things are improving on the mobile side, it looks like this setup is also starting to take shape for those with a Chromebook.
Francois Beaufort has shared some details about using the OK Google command on Chromebooks. For now this functionality is limited to those using the Dev Channel. And furthermore, it is not quite as touchless as one would hope. Not to mention, it is not quite as full featured as one would hope.
That being said, assuming you have enabled the App Launcher Start Page you are good to go. Otherwise, those looking to get this setup can activate the chrome://flags/#enable-app-launcher-start-page flag. Once done, you should then be able to open the App Launcher and say OK Google. The catch here, you will need to manually open the App Launcher before the command can be recognized.
For now this OK Google support is limited to searches. Further details from Beaufort touch on some of the potential though. He mentioned being able to say OK Google, open Gmail, and also using the command to initial chats with specific people. As of now there hasn’t been any timeline as to when this added functionality will be supported. As well, there was no mention of when this will leave the Dev Channel and arrive for all Chromebook users.