Right now, Google Voice's primary function is to provide call-forwarding and message transcription services. That may change, however, with the reported purchase of Gizmo5 by Google.According to a report from TechCrunch's Michael Arrington, informed sources say that Google has acquired Gizmo5 for about $30 million. Gizmo5 was previously a target of Skype, but that has changed with Skype's recent litigation woes.

Gizmo5 lets PC and mobile phone users make free calls over the Internet via SIP technology. This lets users avoid certain fees that they might otherwise encounter using the natural services provided by their network operator.

Gismo5, says TechCrunch, is a fabulous fit for Google's Voice and Talk products.

I use Google Voice to manage which phones ring at different times of the day depending on where I am. By using Google Voice's call forwarding features, I am able to divert calls from my Voice number to whatever cell phone or landline I wish.

In addition to the call forwarding services, Google Voice can also intercept voicemails and transcribe them to email or text messages and send them to the inbox of your choice. Not bad for a (mostly) free service.

Google Talk is Google's instant messaging client that also lets users conduct video chats.

Gizmo5's technology portfolio could be the glue that ties Google Voice and Talk together by adding a soft phone end point for Google phone users and a PSTN link that permits for incoming and outgoing calls to real phones.

Long story short, with this acquisition, Google Voice users may soon be doing more than simply passing calls around the Internet.

Neither Google nor Gizmo5 have confirmed the report.