iOS: Google's updated the Google app with some new features, including a handy, always-on "OK Google" option that gives you detailed answers from the page you're on.
In the new app, you can head to any article you want, then search for contextual answers based on the article. For example, if you're reading a page about William Shatner, you can say, "OK Google, where was he born?" or if you're reading about a location, you can say, "OK Google, how far away is this place?" They also added more detailed local search results, which should make those searches go by a little quicker.
Google (Free) [iTunes App Store]