http://www.engadget.com/2010/11/16/official-google-voice-app-for-iphone-hits-the-app-store/
A few weeks after third-party apps started filtering in, Google's launched its own Google Voice app for the iPhone, and it looks to have all the most important features: call and text support, push notifications, and voicemail access (including transcriptions). It's available right now -- US only at the moment -- on iPhones with iOS 3.1 or higher as long as you've got a valid Google Voice account set up... so get to it.
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