Google has been working on a revolutionary VoIP system known as Google Voice for some time now. Available as a beta version to invited guests only (similar to the way Gmail was first introduced), Google Voice is in its initial testing stages before a major rollout to the public. The latest news surrounding the new service is that Google has acquired internet telephony company Gizmo5 in order to merge the two to enhance the Google Voice service. Gizmo5 is a Skype-like web based VoIP client, which differs only in the fact that it is set on SIP (an open standard) rather than an internally developed system as Skype follows. Currently, Google Voice is not a VoIP service. Rather, it is a way to consolidate multiple phone numbers into a single number which can be dialed out from as well. And it also offers other features such as transcribing voicemails into emails which can be viewed from anywhere with internet access. However this is all done through existing phone networks, perhaps the introduction of Gizmo5 would add a VoIP method of calling for Google Voice users. There is no information on how Gizmo5 will be used in Google Voice as of yet, and no new users can request to sign up for Google Voice until these changes are made.
Here is an official source - Gizmo5 Has Been Acquired by Google This is another Google business model practice. They do always spend huge budget for a lifted up their new business, thus saved a lot of times compared to development by themselves from scratch. I wonder if Google could beat whole "VOIP system" in a soon.
Google is really having hard time beating up such existing businesses but still Google making themselves as one place for most internet application everyone want and need.