Google is a few steps closer to unifying the world's wireless networks—and, in the process, providing your smartphone with a faster, more reliable, and less expensive signal.

Today, Google announced a deal with Three, one of the largest cellular carriers in Europe, that will allow Americans to use its experimental Project Fi wireless service when traveling in an additional 15 countries, bringing the total number of foreign countries where the service is available to more than 135. And at the same time, the company is removing the speed cap that previously limited the service overseas.

Unveiled last year on Google's flagship Nexus phones, Project Fi not only offers a way of making calls over Wi-Fi networks inside homes, offices, and local coffee shops. As you leave Wi-Fi coverage, it can seamlessly and automatically move those calls onto a cellular network. Plus—and perhaps more importantly—it can move phones between disparate cellular networks, depending on which offers the best signal. And it does all this for a small, flat fee.

Initially, the service allowed phones to jump between Sprint and T-Mobile. Then Google added US Cellular. And now, through its deal with Three, the Internet giant has extended the service's reach even farther. "We can now reach about 97 percent of markets where Americans travel abroad," says John Maletis, Project Fi's head of operations. And, he adds, the service is significantly faster in these markets.

Project Fi already provided service in more than 120 countries worldwide via relationships T-Mobile had already established with foreign networks. But in an effort to keep its costs down, Google throttled all overseas traffic to a relatively slow 256 megabits per second. Now, the company says it's lifting this throttle to provide 10 to 20 times faster network speeds for those traveling abroad.

Yes, other wireless services have long provided ways of roaming on other networks, but this often comes at a steep price—a price controlled by a single gatekeeper. Project Fi costs the same no matter what network you're on and no matter where you are: Google charges a standard fee of $10 for every one gigabyte downloaded. That's why it was throttling overseas traffic. Maletis says Google is intent on running Project Fi as a sustainable business, but the company now believes it can do so while offering faster speeds.

Room to Roam

A faster, more expansive Project Fi is good news not only for anyone using this groundbreaking service, but for, well, anyone. The model proposed by Project Fi is how wireless should work. Your phone will connect to the network with the best signal, not whatever signal a lone carrier happens to offer at a given location. Your phone roams based on what's best for you, not your carrier's bottom line. It's an idea that's long overdue, and it's a sign of a larger shift across the world of mobile phones.

On its iPads, Apple now lets you test various wireless services before settling on one. Down the road, the company will surely do the same on iPhones. And Microsoft appears to be moving in a similar direction. Most phones still come tied to a single carrier, but as Project Fi and these others show, it doesn't have to be that way. The technology has arrived to give everyone options.

Not everyone has the option of using Project Fi. Google classifies the project as an experiment, saying it does not intend to become a large-scale wireless carrier. But in presenting a better alternative, Project Fi is meant to push other providers in the same direction. It's similar to Google's approach with its Android mobile operating system and its landline Internet service, Google Fiber. In all cases, the aim is to show the world that a better way forward is possible, raising expectations for everyone. That said, Google now appears serious about turning Google Fiber into a true Internet service provider, as it expands to major cities across the US. We can't help but wonder whether if it will expand Project Fi in similar ways.

At the moment, Project Fi is only available to Nexus buyers based in the US. And Maletis says the company has no plays to expand the service to other phones. But it's telling that Google is building Project Fi as a viable business—and not just throwing money at the problem.

Correction: This story original said that Project Fi charged $10 for every 10GB download. It charges $10 for every gigabyte.