2022 update- this post needs a major update.
So you think you’ve gamed the system and figured out a way to get unlimited free calls from an International virtual phone number to your Google voice which in turn forwards to your cell phone or landline here in the states.
Unfortunately thats not the case. (We still love Google though.)
This would be true if Google voice was an actual VOIP solution. Google doesnt allow any incoming traffic to a users Google voice number unless they dial the number directly. They would need to provide a SIP address in order for Google voice to be called VOIP. A SIP address is sort of a “Internet address” for voice calls, it opens up Google voice to the entire world if they did it.
You can still forward your calls to Gtalk for free and without limits but thats not the same. Gtalk is a soft phone application you run on your PC. However we have had success with the Vtok app ( no longer in service ) on the iPad and iPhone.