I realised about an hour after I posted the question that push notifications are almost exactly the same thing, except that cloud-to-device message APIs is some

I realised about an hour after I posted the question that push notifications are almost exactly the same thing, except that cloud-to-device message APIs is something Google is using themselves to show the power it has, which Apple didn't do. But yes, one could write an app (I think Boxcar is in the best position to do this) that can push "intent"s to iOS devices and open them in the proper apps like it already does with Twitter.