T-Mobile and Google have been working with each other for donkey’s years. (That’s British for: A very long time.) Going all the way back to the T-Mobile G1, the very first Android phone. But they’ve never done anything as ambitious as Project Fi seems on the service.

As rumored many times, Google has finally announced its MVNO carrier. And just like the rumors suggested, you pay for the data you use and not for an ill-fitting bucket that resets every month, or leaves you with a rollover allowance of data you probably won’t ever use. Also, as rumored, the Project Fi carrier uses Sprint and T-Mobile’s cellular networks to connect. But it’s much more than that.

Project Fi uses some clever technology to not just ensure you’re connected to the best cellular network. It connects you to the best network, period. That could be LTE on Sprint/T-Mobile or on Wi-Fi. So – essentially – its default position is to route all your calls, messages and data through Wi-Fi. But if that’s not available, it uses LTE. As explained in Google’s official blog:

“Project Fi aims to put you on the best network wherever you go. As you move around, the best network for you might be a Wi-Fi hotspot or a specific 4G LTE network. We developed new technology that gives you better coverage by intelligently connecting you to the fastest available network at your location whether it’s Wi-Fi or one of our two partner LTE networks. As you go about your day, Project Fi automatically connects you to more than a million free, open Wi-Fi hotspots we’ve verified as fast and reliable. Once you’re connected, we help secure your data through encryption. When you’re not on Wi-Fi, we move you between whichever of our partner networks is delivering the fastest speed, so you get 4G LTE in more places.”

This could be incredible for customers who spend most of their time indoors hooked up to work or home Wi-Fi. It just makes the experience of using a phone more convenient, and billing is incredibly simple too. $20 per month gets you “the basics” which includes talk, text, Wi-Fi tethering and international coverage in 120+ countries. Cellular data is a flat-rate $10 per 1GB, so 2GB costs you $20, 3GB costs $30 and so on. If you don’t use all your data, you get credit back for the unused amount. Google uses the example of being on a 3GB data plan and only using 1.4GB in a month, in which instance, you get $16 credited back to your account.

If you don’t use it, you don’t pay for it.

As of right now, Google is beginning a Project Fi Early Access Program inviting people to sign up for the service. Sadly, it’s only available to customers with a Nexus 6 due to some software and hardware constraints. Google invites U.S. consumers to check its cellular coverage map (which is super-fast and responsive BTW) to ensure you can get a 4G LTE network where you live, work and travel. If you want to find out more about the plan, or read through some FAQs head on over to the “about” page.

International roaming is similar to T-Mobile’s own international deal on Simple Choice. Data costs the same amount ($10 per 1GB) as it does in the U.S., except customers are reduced to “256kbps/3G”. International calls cost 20 cents per minute and texts are unlimited.

By all accounts, T-Mobile is delighted to have Google as a partner on this project. John Legere, in a blog post published recently, expresses his delight at being involved in Project Fi. After waxing poetic about how Google is his “kind of people”, he outlines the benefit for the US market as a whole:

Let me be 100% clear. Not only is this a great opportunity to put the T-Mobile network into the hands of even more Americans who spend their days and nights Periscoping, YouTubing, tweeting and streaming, the brand association is a strong one. It’s been fantastic to pull together some of the biggest brains in tech to drive innovation that could directly benefit tomorrow’s American wireless customers. The carriers have dug in their heels and held US wireless back for too long. This industry needs all the fresh blood and fresh thinking it can get.

On more than one occasion in the past, Legere has stated his belief that wireless is evolving far beyond the traditional carrier. And has even thrown in Google’s name among brands like Facebook when talking about future non-traditional wireless service providers. Project Fi could be the very beginning of this shift towards non-restricted access to wireless communication.

What do you make of Project Fi? Will you be ditching T-Mobile in favor of Google’s new service? Or are you happy with the Wi-Fi calling and unlimited data on T-Mo?

Side note: I really wish we had this in the UK. The amount of time I spend at home in my office, I’d save an absolute fortune.

To request an invite, head on over to fi.google.com.

Sources: Google, T-Mobile