Google has announced via their Office Blog that Google Voice and Sprint are teaming up. Google Voice's availability at Sprint has been limited to cell phones that could support the Google Voice app. That's all changed, Sprint customers can now use their mobile phone number as their Google Voice number.
Adding Google Voice to the Sprint network will allow Sprint customers to use all of the features Google Voice has to offer without having to get a new number from Google Voice or port over their existing number. Sprint is also now allowing current Google Voice users to use their Google Voice number as their primary Sprint phone number. All of this can be done without the Google Voice App.
Google Voice would replace Sprints voicemail system and outgoing international calls would use the Google Voice network and the Google Voice rates rather than Sprints which could end up saving customers a pretty good amount of money on international calls. According to Sprints website, a call to Canada from the USA would cost $0.59 per minute but through Google Voice calls to Canada are free.
The integration isn't complete yet, but when it is, you will be able to enable it through the Google Voice web interface. If you are a Sprint customer and would like to sign up to be notified when it is available, you can go to google.com/voice/sprint.