Google Now is not just a new mobile feature. Google will also offer it on the Google homepage.
Some new source code has been spied on the Google homepage that implies that Google will also bring the Google Now assistant to the Google homepage. So far Google Now has been confirmed only for iOS, Android and Chrome.
Google promotes Google Now on Google.com with the text: "Get started with Google Now. Just the right information at just the right time. Google Now uses your Home location to show relevant information like weather, traffic conditions, and nearby places."