Third party Siri support

New apple store app update enables interfacing with Siri. This seems like a definitive proof that support for third party apps already exists. There is a hope that Apple will enable it in some form to developers sooner rather than later.

http://www.macrumors.com/2012/11/07/apple-store-app-updated-with-siri-and-gift-card-passbook-support-theoretically/