Google's Project Fi now available on Nexus 6

If you have a Nexus 6, you can now use Google's wireless service. The service, called Project Fi, has effectively turned Google into a mobile carrier.

"Similar to our Nexus hardware program, Project Fi enables us to work in close partnership with leading carriers, hardware makers, and all of you to push the boundaries of what's possible," the company said in a blog post last Wednesday.

The service requires a special SIM card, and will work with current, as well as with future Nexus 6 devices. As it's currently an "early access program“, other devices are not supported.

Google sets itself apart from other mobile carriers in a way it charges for the service. Unlike other carriers, which charge you a flat monthly fee that comes with a preset amount of data, with Google you only pay for the data you actually use.

If you fail to use all the data you've paid for, Google will refund you the difference.

"Here's how it works: for $20 a month you get all the basics (talk, text, Wi-Fi tethering, and international coverage in 120+ countries), and then it's a flat $10 per GB for cellular data while in the U.S. and abroad. 1GB is $10/month, 2GB is $20/month, 3GB is $30/month, and so on. Since it's hard to predict your data usage, you'll get credit for the full value of your unused data. Let's say you go with 3GB for $30 and only use 1.4GB one month. You'll get $16 back, so you only pay for what you use,“ says Google.

The company's wireless service will get the help from T-Mobile and Sprint, and the transition from Wi-Fi to LTE and vice-versa should be seamless.

Project Fi phone numbers "live in the cloud," according to Google, enabling you to text and place voice calls from a laptop or tablet without your actual phone nearby.

If you're interested in being part of Google's mobile experiment, head over to the signup page.