We've seen several third-party Google Voice iPhone apps make their way into the App Store, but we'll be seeing Google's official version soon too according to a report by TechCrunch. Apparently Apple may have even approved the app already:
[TechCrunch has] gotten word that the official Google Voice application is on its way to the iPhone in the next few weeks. In fact, [they've] heard from a source close to Google that it's already been approved - Google just needs to revamp the application to work with the iPhone 4 and iOS's multitasking capabilities.
Sounds like great news, particularly since an official Google Voice app could include features which third-party versions are unable to offer due to API limitations. [TechCrunch]