If you are outside of the US, Google Voice is merely a service to place calls from inside... apparently just GMail and Hangouts, much like Skype is. Unlike Skype the quality of service seems to be good. Also unlike Skype, though, I can't figure out how to make this happen from my Nexus 7.
When I try to add a phone number to an hangout, the Hangouts app on Android tells me it doesn't know about that number and proposes to send an invitation text message. Of course this happens even when I put in my own mobile number (which afaik is connected with my Google account) and from what I can tell the sending happens from the device itself - and thus obviously fails.
Is this something that can be done?