Package up voip.ms or anveo on the backend in a nice UI, and provide a reliable SIP app (e.g. sipdroid), and you basically have what you guys are going for. If

Package up voip.ms or anveo on the backend in a nice UI, and provide a reliable SIP app (e.g. sipdroid), and you basically have what you guys are going for. If you focus on polish you can probably charge a premium, as right now there's still a high tech factor involved in setting such a system up.