not sure what calling from google voice to IPKall would accomplish...
I use IPKall to get a free incoming phone number. Then I use Google voice to make a free outgoing telephone call to wherever.. but Google Voice has to call you in order to make a call, which is why I have to use the IPKall phone number- to receive the Google Voice "outgoing" call
Dial number in Google Voice -> Google Voice calls my IPKall number -> I get 100% free outgoing calls
Since people can also call you at the washington IPKall number, you get free incoming/outgoing phone service like this
Unforunately, the Google Voice calls fail to connect most of the time. I have to attempt the call many times before it works and sometimes it even blocks me from trying again. I think they may have something programmed to attempt preventing people from doing this kind of thing, because I know there used to be some other website that let you set this same kind of thing up, but then Google bought them and shut it down.
Or maybe the IPKall numbers just don't work very well. I haven't used it much for incoming calls so I don't know