Yes, they do - CloudSoftPhone. I just played with it. The problem for me is that it is entirely data/VoIP based. Unlike GV, where your cell phone would actually call their proxy via the phone (not data), this one relies entirely on your carrier's data coverage. Which, for T-mobile in Tampa, is very hot and cold.
Where it works, it works great (40+ mpbs) but, 10 feet to the left, and you get zero data. It makes using it for audio/video the pits.