Continuity is one of the best things about going all in on Apple hardware. With it, you can easily send and receive calls or text messages from your Mac or iPad — even when your iPhone is in another room. But one requirement of using Continuity is that both devices must be on the same Wi-Fi network. With iOS 9, that's set to change, and T-Mobile wants the world to know it's the first major US carrier to offer Continuity through its cellular network. Based on screenshots of the first iOS 9 beta, you'll need to have Wi-Fi calling switched on to get this feature, but once that's done you'll be able to participate in conversations on your Mac or iPad no matter what Wi-Fi network they're connected to.
Update: Read the iOS 9 review.
It sounds like a small change, but it's definitely a convenient one. If you were to accidentally leave your iPhone at home, you'd still be able to answer calls and messages from your Mac laptop at work, for example. Moving Continuity to cellular networks basically means you'll never be out of reach when working on an internet-connected Mac or Apple's tablet.
T-Mobile is already supporting this feature for developers running the iOS 9 preview build; many more people will be able to try it out once Apple launches a public beta of the update next month. But it's very doubtful that T-Mobile will stand alone by the time iOS 9 launches to all consumers this fall. At that point, you can expect to see many big mobile operators add support for Continuity over cell networks.
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