New York: T-Mobile US Inc. is now letting customers link their phone numbers to any other internet-connected device—tablets, laptops, or work-assigned phones—through a new app called Digits.

With the service, T-Mobile is targeting consumers who want to use their 10-digit phone number to send and receive text messages using their computers and tablets as well. Digits will also give some of the 30 million people who carry two phones—business and personal—the option to use just one, according to chief operating officer Mike Sievert.

Starting on 31 May, all T-Mobile phone numbers will be portable at no extra charge, and subscribers will have the option to add a second Digits phone number for an additional $10 a month. The Bellevue, Washington-based company is introducing the service after a five-month trial.

Today’s mobile phone users talk and text using devices that are assigned a specific 10-digit phone number programmed into SIM (subscriber identification module) cards. As more daily communication has moved over the internet, web-based applications apart from the nation’s phone network, like Facebook’s WhatsApp, Google Voice and Microsoft’s Skype, have taken off. Now calling, video-chatting and texting within a single app are commonplace.

T-Mobile’s Digits, which has been in development for two years, is designed in part to capitalize on the popularity of those apps. “T-Mobile said ‘we can do that too’," said Roger Entner, an analyst at Recon Analytics LLC.

But there’s a security risk. “The moment you make your phone an app you make it potentially vulnerable to hacking," Entner said. “You are trading a little security for convenience."

T-Mobile’s Digits app requires two-factor authentication, meaning customers must enter a log in and password. An authorization code is sent to a device the first time Digits is activated.

The service will be enabled on all T-Mobile accounts, but customers won’t be forced to use it. Bloomberg