Google announced Project Fi not too long ago. It's basically their way of getting into the MVNO business, which for those that don't know what that is. An MVNO is a Mobile Virtual Network Operator. You're basically paying one of the carriers to use their towers and network. Similar to what Straight Talk does. What's unique about Google's Project Fi is that it switches off of T-Mobile and Sprint's network, as well as WiFi. So you never have to worry about connecting or disconnecting from WiFi. It automagically switches for you. It's pretty nice. However, Project Fi only works on the Nexus 6 at this point. It'll probably work on the Nexus devices that are coming out at the end of the year to launch with Android M, as well.
So far, Project Fi is invite only, with a select few having gotten their invite already. Google has updated their Project Fi site a bit. So that you are now able to track the status of your invite. Mine says "Invite Status: We're still determining your status. Check back here for updates." Others are seeing "3-4 weeks", so who knows how Google is prioritizing these invites, it could be location based as well. Which would explain a lot actually. Especially if they are looking to go nationwide without invites fairly soon.
Google's Project Fi doesn't give you unlimited data. Instead you pay for each gigabyte. However, whatever you don't use, gets credited to your account. So if you pay for 3GB of data at $30, and only use 1.4GB, you'll be getting $16 back. They don't round it up to the nearest gigabyte, which is definitely nice to see.
You can check out the status of your Project Fi Invite here. It's pretty interesting that you can check the status, can't say we've ever seen that before for a new product that uses invites. Maybe OnePlus can do something like this for the OnePlus Two, as they told us earlier this year that we will be seeing the invite system return for the launch.