There were apps to do this a long time ago, at least 3 years ago I remember texting and voice calling with the first iPod touch with retina screen with a VoIP app. I forget the specific app name though, and the mic wasn't that great. I remember calling someone and they said that they couldn't really hear me, but they guessed what I had called them about anyway because of the specific time. Google's apps might be more convenient than the app I used and/or cheaper, but they weren't the first.