T-Mobile has announced it plans to officially launch its "Digits" program on May 31 after a successful beta that began late last year. The service combines features of services like Google Voice and AT&T NumberSync into a single product, by allowing customers to use their number on multiple devices, as well as creating additional numbers that can be shared between family members or used as a burner line.

Digits works through the web as well as standalone iOS and Android apps, though recent Samsung phones and the LG G5 have native integration for Digits in their existing dialers. You make and receive calls as well as send and receive text messages on all connected devices, and much like Google Voice, it’s possible to customize which devices should ring whenever there’s an incoming call.

All T-Mobile phone numbers will automatically become Digits and customers will be able to use them across devices for free. Additional Digits lines are available for $10 per month, though for a limited time, customers that subscribe to the $5-per-month T-Mobile One Plus — which offers extra features like a mobile hotspot and in-flight Wi-Fi — will get an extra Digits line at no additional cost.

T-Mobile mentions a few scenarios where you’ll appreciate having this new functionality, like still being able to make or receive calls from another connected device if your phone’s battery dies or you accidentally left it at home. With an extra number you can also keep one for personal use and another for business instead of lugging two devices around. This is something Google Voice users have been able to do for a while, but T-Mobile is letting customers assign up to five numbers to a single account.

Families could also share a Digits number as their home number shared across everyone’s smartphones, or for any other situation where you may not want to pass along your personal number, you can keep an extra number as a burner line for improved security and privacy.