That said, Google Now will work quite a bit better for you if you use Gmail, and Google Calendar. And, from the video, it looks as though Google Now would come as an update to the Google Search app for iOS, which had gotten the voice search capabilities fairly recently. Once the update hits, the Search app would have Google Now available as a swipe up from the bottom, and would be able to give you weather, navigation, sports scores, reminders, and a ton of other content.
Of course, the video that leaked was pulled pretty quickly, which doesn't really mean much except to say that Google isn't quite ready to make the announcement. The videos look legit, so it's probably just a matter of time before Now gets added to the iOS Google mobile phone Search app.