You get a lot more integration than you probably think with Google Now. It reads my e-mail to keep track of my upcoming flights and packages being delivered. It checks out my calendar and will conveniently provide directions to events on my schedule. There's not a great level of integration for the google chat and voice features yet, but it's coming I'm sure.
Yeah, I guess if you want 3rd party integration via an API you're probably looking for Apple's Passbook. It'll be interesting to see what MSFT does here and how long it'll take for all three to merge into a similar set of features.
