T-Mobile's Digits feature, which turns all T-Mobile subscribers' numbers into virtual numbers, will go live on all T-Mobile subscribers' accounts on May 31, the company said today.

That will give every T-Mobile subscriber the ability to check their text messages and voice mails from PCs and Macs, and the potential to use their phone number on multiple devices or to have multiple numbers on one phone.

"You can now take your primary T-Mobile number and use it across a variety of devices," T-Mobile COO Mike Sievert said.

We have a full preview of Digits from when we tested it in December. (Sievert says T-Mobile has worked out the bugs I saw.) The news today is the launch and pricing, and it's a little confusing, if only because Digits is a new concept.

Digits does three things. It gives you an app and a web interface to get into your calls, text messages and voice mails from a PC, Mac, or another phone with a downloadable app. That's free.

It also lets you add your existing number to other devices. If the device doesn't already have a T-Mobile line of service, that will cost $10 for slow data speeds of 512kbps, or $20 for full data speeds. You'd use this feature with a smartwatch or tablet, or if you had a second phone you want to add your number to, like a weekend dumb phone you're using at the beach.

Finally, it lets you use additional numbers on your existing phones. That will cost $10/month per number, with one number included if you're on a T-Mobile One Plus plan. You'd use this option if you want to have business and personal numbers on one phone, for example, or if you want a number to give to online dates.

I use Digits myself to access my text messages on my work PC. Especially if you end up in a long text-message conversation and would rather type answers out on a big keyboard, it's very helpful.

Digits Goes Broader

No other carrier in the world is doing anything like Digits right now, T-Mobile CTO Neville Ray said. The technology is based on common industry standards and some T-Mobile patented ideas, and other carriers are looking into it, he said.

"There's a ton of interest, especially coming out of the European market, already," he said.

Part of Digits's broadening will be integrating it into more smartphones. Right now, recent Samsung phones and the LG G5 can integrate multiple Digits numbers directly into their dialers. Other phones have to use a downloadable app to dial or check messages with their secondary numbers. A software update for the LG G6 will enable the feature on that phone, Sievert said.

But of course, Digits will really take off when it comes to iPhones. Ray expressed hope that would happen soon. "It's not a huge leap. We've got the Apple bridge to cross, and that will come," he said.

T-Mobile customers can activate their Digits lines at t-mobile.com/GetDIGITS.