yami,
You will not be needing a VPN once you set up Google Voice. If outside tht USA the only time you might need to use a VPN with a USA ip is to setup a Google Voice account. Another hurdle you will need to overcome is the inital confirmation call back that GV requires to activate the service. You need to figure out the following two things from your country of origin:
1) How to use a VPN service which will give you a USA ip for the registration process
2) How to get a US telephone number to Call forward to your local telephone number
Canadians also must be creative in order to get a GV telephone number. I explain one way how to do it. If you get a DID number from a voip service provider in the US and don't mind paying the cost of a long distance call to your local telephone number, you might be able to use some of the ideas contained in this thread originally written for Canadian reisdents. You need to make certain that the SP offers unconditional call forward to your long distance tel number.
I think I have read some people not being able to use GV in their country outside the US. However there are also many people reporting success in many parts of the world. You will need to try it out for yourself. Perhaps you can ask on this forum if there are any other OBi users who have setup GV in your country and how they setup the account from outside the US. The simplest way, it seems to me, is to ask someone in the US to setup an account for you if that is at all possible.
This is my thread for setting up GV in Canada. It may help you get some ideas.
One time charge of $50 for a SIP Acct at freephoneline+How to setup GV in Canada
http://www.obitalk.com/forum/index.php?topic=93.0
