The "Ok Google" command has expanded since the debut of Android KitKat, allowing devices to respond in various smart ways to those two words. Now, Google Maps on Android has this ability too, whether you're in the middle of a road trip or doing something else. Once it's enabled in settings, you can choose whether it works only while Maps is open or from any screen. Say the magic phrase then follow it up with something like "find a gas station" or "How's traffic ahead?" and it will let you know.
Existing Google Maps voice commands like "What's my ETA?" work too, plus new addition like the ability to turn traffic display on or off. You can control whether or not the phrase works on your phone via settings in the Google Search app (make sure you have the latest version for that and Maps first), to turn on "Ok Google" everywhere, or just in Maps, if you'd prefer it that way. You can find a list of commands here, or just give it a try and see what works.
Whether or not you use the voice commands, it's another example that while the Google Now / Now on Tap branding may be taking a backseat, the features are actually spreading further throughout the OS. Google's new Assistant AI helper is built around conversational responses to any "Ok Google" query, and we're expecting to hear more about it during the October 4th "Made by Google" event.