How do you use Google Voice instead of built-in text message with Siri on iPhone4S?

Question

I would like to use the Google Voice app instead of the built-in Text Messages with Siri on the iPhone 4S.

Is this possible and how?

Answer 1

No, it is currently not possible for Siri to use other apps than the ones it already integrates with.

Source: Daring Fireball (paragraph 9, or ⌘F “there are parallels”).