Loren Brichter on XPC, one of the new APIs in OS X and iOS:
I can’t fathom the extent of the innovation we’ll see, but even simple things that are impossible now like third-party apps sharing bits of themselves with other apps will be possible. I can also envision faceless apps, doing neat things for you in the background without presenting any UI and using minimal hardware resources. It can make third-party apps peers to the system-level Twitter and Facebook integration of today. We may also see much more ambitious apps, as Apple may relax some of their rules regarding arbitrary code execution, as long as you run the code in a super-sandboxed XPC process. That’s the one that has me really excited.