Customers can ring one number on up to five devices.
T-Mobile is moving forward with its effort to allow phone numbers to be assigned to more than one phone or other mobile device.
Starting May 31, the carrier at no charge will allow customers to assign one number to ring on up to five phones or other portable devices like a tablet or smartwatch. The service, called Digits, also lets customers send and receive texts using the number via those devices or a computer’s web browser. And customers can assign up to five numbers to a single phone, with each additional number costing $10 per month.
The new system in some ways resembles services from Google googl , Microsoft’s msft Skype, and others that allow users to make and receive calls on multiple devices with one number. But T-Mobile’s solution, which has been in a beta test since last year, uses the core phone network and doesn’t rely on workarounds that mess up caller ID and other telephony functions. Still, using Digits requires a special app on most phones–so far it’s only compatible with the native dialing app on Samsung Galaxy smartphones and the LG G5.
T-Mobile’s chief operating officer Mike Sievert lays out a host of common use cases where Digits might come in handy. Instead of having a landline at home, a family could share its “home” number on all its mobile phones, he says. When a call comes in, all the phones ring and whoever answers first gets the call. Or, businesses could hand out a Digits number to an employee. The employee could assign the number to their current phone, ending the need to carry both a personal and business phone.
Get Data Sheet, Fortune’s technology newsletter.
Over 40% of customers in the beta test also used Digits to send text from their computers, he says.
“One thing that caught our attention is how many people were using their Digits on a PC or Mac,” Sievert says. “There’s something about being able to out-text your friends with a real keyboard.”
T-Mobile tmus will also allow customers to purchase temporary numbers for a one-time fee of $15. That could come in handy for using on a Craigslist posting or giving out at to someone you meet at a bar, Sievert says.
At the start, T-Mobile said subscribers for its premium unlimited data plan, T-Mobile One Plus, will get a free second number to use with Digits.