Google (Nasdaq: GOOG) has added to its services portfolio with the acquisition of a unified communications startup, GrandCentral Communications , for an undisclosed sum.

GrandCentral, which is still in beta trials, has developed a softswitch-based service that provides users with a single phone number that, when called, will ring all or any of the subscriber's devices -- mobile phone, home phone, work phone.

Using a Web portal, subscribers can choose which of their phones should ring when their single number is called, and even set up rules determining which devices should ring depending on who is calling. Calls can also be switched from device to device without the need to restart the call session.

The GrandCentral system also allows users to converge all their voicemail inboxes into a single account that can be accessed from any of their devices or via the Web. Users can also listen to voicemails as they are being left.

The technology developed by the GrandCentral is married with a VOIP service from Global Crossing (Nasdaq: GLBC) to create the beta service. (See GLBC Adds Customer.)

The company was set up in late 2005 by Craig Walker and Vincent Paquet, who were running Skype rival Dialpad Communications when it was acquired by Yahoo Inc. (Nasdaq: YHOO) in June 2005. (See Yahoo Enters VOIP Fray.)

But they didn't stay at Yahoo long. The GrandCentral Website notes of the duo that "they suspected there were other problems that could be solved using next-generation communications services and both missed the intensity of the start-up environment." In a statement posted on its corporate blog, Google says GrandCentral's "technology fits well into Google's efforts to provide services that enhance the collaborative exchange of information between our users."

At the heart of those efforts is Gmail, and that's the service Ovum Ltd. analyst David Bradshaw believes Google will hook up with GrandCentral's capabilities. "Integrating it with Gmail is the obvious thing for Google to do, and that could just be the killer move," notes Bradshaw, though he remains unconvinced of the broad potential of unified services. "I'll need a lot of convincing that GrandCentral will do any better than the former Unified Messaging vendors prior to the dot.com bust," he writes in a research note issued today.

GrandCentral was backed with an unknown sum by Minor Ventures, a finance house run by Halsey Minor, best known for founding CNET in the 1990s and being an original investor in Salesforce.com Inc.

GrandCentral is just the latest in a string of acquisitions made by Google in the past few years. (See Google Acquires Panaramio, Google Acquires Feedburner, Google Acquires DoubleClick, Google to Buy YouTube, Google to Target Us With dMarc, and Google Buys Ad Firm.)

— Ray Le Maistre, International News Editor, Light Reading