30 minutes ago I found Talkatone. I came across it because I'm wanting to make phone calls from my LTE-equipped iPad 3. Honestly, I thought when I got around to this, I'd just use the Google Voice app the same way I make calls from my GMail account on my desktop. Apparently it's much more complicated. On my Android phone it was just a matter of asking an automatic dialog that asked if I wanted to use Google Voice instead of T-Mobile for my calls. Of course being a totall Google Voice fan I said yes. Is this because Apple doesn't want GV to work on the iPad? Hmm.
Anyway, Talkatone seems horribly complicated. But I'm sure it's the kind of thing where it makes more sense the second and third times you read the docs.
PS: And then I came across this. :-)