Google Voice is now available as an application on BlackBerry and Android phones, before the product is made available to the general public.

Google Voice is Google's attempt at uniting all of a user's communications devices behind a single number. Through one phone number, users can link various numbers; work phone, home line, cellphone.

When Blackberry or Android users call from their phone using the app, the receiver of the call will see the user’s Google Voice number, instead of their mobile phone number. The same applies to text messages.

Voice mail will also be forwarded to all of the phones, along with a free transcription by Google. Users can also make international calls from their handset with Google's calling rates which they claim are cheaper.

Google, which first announced Google Voice in March, is gradually giving numbers to people who request it. According to Vincent Paquet, a Google senior product manager, the company began releasing tens of thousands of numbers a day to fulfill those requests.

In fact, demand to try out the Google Voice has become so popular that invites are being auctioned for as little as 99 cents to as much as $100 on eBay.

Blackberry and Android users can download the app from the Google Voice mobile site at m.google.com/voice. It has also been made available in the Android Market by searching for Google Voice.

Below is a video showing how Google Voice works:

Google Blackberry Software Android