Google Voice -- the search giant's VoIP call-routing service -- is now available in Android and BlackBerry applications, offering users a centralized platform handling a unified phone number, SMS, and automated voicemail transcription.

The service functions primarily around connecting users' traditional phones via VoIP. The technology, based on Google's acquisition of GrandCentral Communications, first appeared as a Google product in March, when it entered a public beta. At that time, users could only initiate calls through a Web interface, which connected the two parties.

Now with Google's (NASDAQ: GOOG) mobile apps for Research In Motion's (NASDAQ: RIMM) BlackBerry and Android handsets, users simply make the call directly from their mobile phone.

"With this new mobile app, you can make calls and send SMS messages with your Google Voice number directly from your mobile phone. The app is fully integrated with each phone's contacts, so you can call via Google Voice straight from your address book," Google Voice Product Manager Vincent Paquet wrote in a blog post.

Google Voice apps will also let users use their smartphones to access and manage their inboxes, make and send SMS messages with their Google Voice number, make low-priced international calls at rates Google said were typical for to Voice over IP (VoIP) services and customize how calls are managed.

"You can choose which calls you'd like to place through Google Voice," a Google spokesperson told InternetNews.com. "On the Android application, you can choose to route all calls through Google Voice, only international calls, or no calls, if you just want to check your voicemail through the app. On the Blackberry, you can simply use the native Blackberry dialer if you do not want to place a particular call through Google Voice."

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