Google's Project Fi is a pretty interesting MVNO. It uses three different networks - US Cellular, Sprint and T-Mobile - and intelligently switches between them and WiFi, as well as public WiFi Hotspots. Project Fi costs $20/month and data will cost you $10/GB. The good thing about Project Fi is that you get reimbursed for the data you did not use. So say for instance you sign up for a 5GB plan, which would be $70/month and you use just 2GB. You'll get an account credit for $30. If you go over the amount that you have on your plan, you won't be charged any crazy fees, prices stay the same, at $10/GB.
One of the features that users have wanted Google to add into Project Fi has been group plans, or family plans. Well those debuted today. Google is offering additional lines for as little as $15/month per line. Allowing you to move your entire family on over to Project Fi and save a bit of cash on the plans that the major carriers are currently offering. Data is still priced at $10/GB, which is pretty impressive. However it is in a data pool, so all users on the plan will be using the data, which doesn't really matter much, since you get reimbursed for what you don't use. Project Fi users are also able to roam in most countries at the same price, just a bit slower data than you'd experience here in the US.
Project Fi is a pretty sweet carrier to use, especially if you're on WiFi most of the time. However, the biggest caveat with Project Fi is the fact that it is only compatible with a handful of devices. Like the Motorola-made Nexus 6, Huawei-made Nexus 6P, LG-made Nexus 5X and the new Pixel and Pixel XL smartphones. As long as you have one of those five devices, then Project Fi is pretty impressive. They also support 4G LTE tablets, so you can add a tablet to your plan and use that data as well. Head to the link below to learn more about Project Fi's new Group plans.