Google is preparing to launch a new service called Google Voice that is built with technology obtained through its 2007 acquisition of Internet telephony company GrandCentral. The Google Voice service gives users a single phone number that can seamlessly route calls to their existing phones. It has its own built-in voicemail service that can be accessed from any phone or through a browser, with GMail-like archiving features for audio messages.

The Google Voice service launched in March for closed testing with a limited audience that consisted of existing GrandCentral users. Google introduced a number of highly impressive features such as automatic message transcription and free SMS delivery. The transcription feature will convert voicemails to text and make them searchable. The service can also automatically forward voicemail transcripts directly to your preferred e-mail account.

There are signs that Google is preparing to open the service to a broader audience. Reports indicate that Google has recently obtained over one million new phone numbers from backbone operator Level 3. PC World speculates that the number grab could be a prelude to the full public launch of Google Voice, but it was unable to get official confirmation from the search giant. There are also reports that Google will offer number portability, enabling consumers to move their existing phone numbers to Google's infrastructure.

Ars recently began testing Google Voice as part of the closed beta program. The service is remarkably powerful and easy to use. It has a number of killer features, such as support for switching between lines during the middle of a call and recording incoming calls by simply pressing a button. Recorded calls and voicemails can be heard directly in the browser through a streaming playback interface and can also be downloaded as MP3 files.

It also offers a simple scheduling system that can be used to control when calls will be routed to specific numbers. For example, you could configure it to direct calls to your work phone during the day and your home phone on evenings and weekends. Google Voice also integrates with your Google address book and allows you to configure different greetings and forwarding destinations for various groups. Call screening is supported with the ListenIn feature, which allows you to hear a voicemail as it is coming in and enter the call by pressing the star key.

The service is off to a good start and already feels relatively mature despite the fact that it hasn't opened broadly to the public yet. Although we're strongly convinced that Google Voice has the potential to be a winner, there are some limitations that detract from its current appeal. The most disappointing bit is that call recording doesn't work on outgoing calls at the present time.

The user interface is consistent with the rest of Google's ecosystem, so it's easy to navigate and very search-centric. The transcription functionality is far from perfect, but it works well enough to consistently convey the gist of a message, if not the exact words. It's a compelling addition to Google's lineup and has the potential to get a lot more interesting as Google integrates its capabilities into its Android smartphone platform.