Back to iPhone Handoff on iOS 27, which 9to5Mac set up live between an iPhone 17 Pro and an iPhone 16 Pro with no SIM in it. The whole setup took about 45 seconds, and the demo settles how the line behaves: both phones carry the number, but only the one you last opened past the Lock Screen is live.
It starts under Set Up Cellular on the second iPhone, with a new option to use the number on this iPhone and another; you pick which phone is the main one, the eSIM stays where it is, and the carrier's own page finishes the sign-up. Both phones need the same Apple Account, Wi-Fi network, iMessage and FaceTime sign-in, and eSIM support, which the channel says reaches back to the iPhone 11. iPhoners on T-Mobile and Deutsche Telekom got it at launch; Verizon and EE are next on Apple's list, per MacRumors.
The two phones never ring together. Opening the second one moves calls, SMS, RCS, voicemail, cellular data, and hotspot over to it, and a test call placed from the 16 Pro went through normally. iMessage stays in sync on both through iCloud, while SMS and RCS land on whichever phone is live. Location sharing follows the active iPhone and Apple Pay works on either, but the Apple Watch stays paired to its original iPhone. Apple's documentation caps it at two iPhones, dual eSIM lines each enroll separately, and Android is out.
9to5Mac reads it as groundwork for the iPhone Duo, a second iPhone that stays home while the Pro and the watch go out, and the watch rule fits. Anyone hoping for two live phones should know it's a switch, not a mirror: the phone in the bag goes quiet the moment you open the other one.
