Update 12/09/16: T-Mobile has informed some beta registrants of a vulnerability on the sign-up site that exposed their personal information to other users.

T-Mobile is no stranger to shaking up the mobile world, having previously unveiled unlimited video streaming, streamlined data plans hassle-free device upgrades. Now it has a new Un-carrier trick up its sleeve: a single number for all your devices multiple numbers on a single device.

Called Digits, the program lets you share your T-Mobile number with any Internet-connected device, including smartwatches, computers, tablets. As the company explains in its press release, “st log in , bam, your call history, messages, even voicemail are all there. And it’s always your same number, so when you call or text from another device, it shows up as you.”

The impact on you at home: You don’t have to be a high-powered CEO or a tech journalist to want your number to work on different devices. might not be making as many calls as we once did, but we use our phones to communicate on the go more than ever, Digits is certainly an interesting idea. It remains to be seen how well it will work in practice, but on paper, it seems as though T-Mobile has developed a system that could truly upend the carrier method.

More numbers, less problems

This isn’t a Bluetooth method like iOS’ Continuity, nor does it necessarily require the device to have a SIM card or cellular chip. th Digits, T-Mobile’s engineers built “an entirely new IMS (IMultimedia Subsystem) service management layer Identity Management solution” that is device agnostic, all but eliminating the need to swap out SIMs to change phones.

so part of the Digits program is the ability to use multiple numbers on the same phone without needing a mess around with a dual-SIM device. T-Mobile claims you can “seamlessly switch back forth between your numbers” specifically touts the plan as a boon for businesses: “You’ll be able to share Digits among employees, so your entire sales team can get both calls texts to your company’s sales line—no more missed sales calls. And if an employee leaves, the business will be able to keep the employee’s Digits number along with any business contacts relationships.”

The service syncs your call log across all of your devices, T-Mobile promises that your extra numbers are just as secure as using a main phone line. Additionally, it boasts carrier-grade call quality over -Fi, beyond what you’ll get using Voice or some other VOIservice.

at’s the catch?

It all sounds too good to be true, but there are some caveats. For one, it’s in a limited beta, existing T-Mobile customers need to sign up to gain access. For another, the experience will vary widely across devices. The tech has been natively built into the dialer on newer Samsung phones (Note 5, Galaxy S6, Galaxy S7), but all other users will need to access the service through the Digits app, or via the web on a or Mac. And for ione users, the Verge reports that the service isn’t compatible with iMessage, which will likely be a deal-breaker for many Apple fans.

The Digits beta is open to T-Mobile’s postpaid customers running a device with Android 5.0 or iOS 9.0 ( newer), or Mozilla Firefox or Chrome on a Mac or . ile in beta, the service will be free to users, but customers will eventually need to pay an additional fee in order to use it. T-Mobile has yet to announce pricing.

Update 12/09/16: T-Mobile has begun notifying a “small number of customers” about a vulnerability on its registration site that exposed personal information to other visitors during the sign-up process. According to T-Mobile, the disclosure was limited to the information input on the site—name, phone number, email address— did not compromise the security of its customer database. The company has “since set up an alternate secured registration process implemented fixes to safeguard your information,” is asking all affected customers to re-register using the new site.