How to set up iphone 3G with no sim to use google voice as secondary phone?

I have an iPhone 3G that does not have a sim (upgraded to iPhone 3GS) I would like to turn it into a secondary phone that uses my google voice account. I also have a sipgate account if needed. Im just wanting to use it as a secondary phone to use on my wifi. . How would i set this up or would i need something else to?|||it is very easy


just follow the instruction there are two ways you can do it


you also need voip app on your iphone siphone is very nice and free from cdiya