“Google says Project Fi will offer new technology that ‘gives you better coverage by intelligently connecting you to the fastest available network,’ whether that’s a cellular network or a Wi-Fi network. The service works with existing cellular networks from US carriers Sprint and T-Mobile, and according to Google, it can automatically connect phones to more than a million open Wi-Fi hotspots that it deems fast and reliable. A flat $20-per-month fee provides unlimited calls and texts, including when you travel outside the country. You pay $10 per gigabyte of internet data sent and received across the network. If you don’t use your entire gig, you receive a credit.”
http://www.wired.com/2015/04/google-unveils-wireless-service-bridge-cellular-wifi/