The ability to use multiple languages with Google Now recently began rolling out to all users, and one of the coolest things about it is that the app can tell when you switched to a different language and react accordingly. As it turns out, this ability extends to different accents as well, as this video from Redditor shadow321337 shows.
To be clear, English (UK), English (US), and other variants are, in Google's eyes, different languages. The same goes for variants of Spanish, Portuguese, Arabic, and other languages that are spoken worldwide. Still, it's amazing to see that Google Now can detect the "language" from the user's accent, even when it's just a short question like "How long is the Golden Gate Bridge?" And everything happens on the fly, which is no trivial task.
To test the feature for yourself, you need to select the primary and secondary languages from Search > Settings > Voice > Languages. If you can't select multiple languages yet, it's because the feature is activated server-side for each user; you'll just have to wait for Google to enable it for you.