Google has just announced its long rumored MVNO service Project Fi. Project Fi is a product of Google's partnership with two US based carriers, Sprint and T-Mobile and relies on their infrastructure in addition to WIFI networks to keep subscribers connected.
The Project Fi offers a $20/month plan that offers unlimited domestic calls and texts, unlimited international texts, affordable international calls, WiFi tethering, and roaming in over 120 countries. Data subscription on Project Fi costs $10 for 1GB, $20 for 2GB and $30 for 3GB. Any unused data left at the end of the month, is reimbursed to the subscriber.
As of now the Project Fi is available to Nexus 6 users in the US and requires an invite to join. Those Interested in signing up can do so by requesting an invite using this Page. You can also use this link to check the coverage areas.