Pretty cool concept. They only offer one phone right now, the LG Optimus, and it relies primarily on WiFi calling with Sprint as a backup. You have to keep your usage within certain parameters, but if you are on WiFi at home and work, you should be good. The phone automatically and seamlessly switches between wifi and cellular, even when you are using the phone. I want to give it a try, but the wife is skeptical. I would be sad to leave windows phone, but to save $100 a month on two lines, I can make sacrifices.