Google Voice can act as your only number — on Sprint phones

Google Voice, the search giant’s very useful Internet-calling application, has just removed one large reason some people hesitate to use it.

At least, on Sprint phones.

Google and Sprint said they will soon start offering (they didn’t specify a date) an option to let you use your Sprint mobile phone number as your Google Voice number. In other words, Google Voice no longer requires you to sign up for an extra number in order to use it. There are all kinds of reasons this makes Google Voice a no-brainer to use — if you’re a Sprint subscriber. To begin with, it will make it easier to save money while making international calls. And it replaces Sprint’s old-school voicemail with smart voicemail that forwards to your email and transcribes your messages. When it does launch, the feature will be gradually rolled out to customers.

As elegant as Google Voice is (I raved about it when it first came out, and still think it’s a must-have application), the one thing I feared might slow its adoption was that the need for an additional number. While not that much of a hassle, it was still enough to make people think twice. To use Google Voice, you’d have to enter the Google Voice online dashboard and choose where to route calls.

Starting today, if someone calls your Sprint phone number, you can set up Google Voice to have the call not only ring your Sprint phone, but also up to five other phones, including your home, office or other cell phones. All the existing Google Voice features otherwise remain the same: You can have the number ring different phones based on who is calling, and what time of day they are calling, and so on.

In addition, if you already have a Google Voice number, Sprint will let you replace the Sprint number issued with your new phone with your Google Voice number. If you make calls or text from that phone, everything is done through deep native integration with Google Voice. So Google Voice will replace your voicemail features — for example, letting you forward voice messages in the form of emails or texts. You can create custom greetings, and customize it for individual callers or groups of callers.

For people who make international calls, they don’t have to switch over to use another cheap phone service. Since the international call is routed through Google Voice, they get the low rates Google Voice offers. This gives Google Voice a leg up over competing services like Skype (it’s true that if you download the Skype application on smart phones, Skype allows itself to be selected as an option to call through — but even the extra step is a nuisance).

The service will also be supported on so-called “feature phones” — the basic phones that lack sophisticated Web browsers, modern app stores, and other distinguishing elements of smartphones like Apple’s iPhone and Google-powered Android models. For phones that don’t offer email, for example, it lets you do things like press “1” to connect to voice mail, and you can select to get a transcript via SMS.

The service can be used by the almost 50 million U.S. users of Sprint phones, though won’t be supported on Sprint corporate accounts or third-party services that rent out Sprint’s network for now.

The companies will demonstrate the new integration on stage at the CTIA conference in Orlando this week.