Apple Launches iPhone Handoff for 2 iPhones as T-Mobile Charges $5 a Month

Q: If unlocking a secondary iPhone transfers your number, what happens to your cellular Apple Watch that stays paired to the primary device?

Your cellular Apple Watch does not follow the number when iPhone Handoff switches it to the secondary iPhone. Apple says the watch stays paired to its original iPhone, so unlocking the second phone does not automatically re-pair or transfer the watch. In practice, that means the watch continues to depend on the iPhone it was originally linked to. If that paired iPhone is nearby, the watch should keep working through it as usual. If the paired iPhone is not nearby, the watch can still function over Wi‑Fi or its own cellular connection, if activated. The catch is that some experiences are still tied to the paired iPhone relationship. Apple notes that if the watch has neither Wi‑Fi nor cellular available, then calls, messages, notifications, some health and fitness features, Siri, and other app functions relayed from the paired iPhone may not be available. Apple’s own guidance is to pair the watch with the iPhone you use most often. During setup of iPhone Handoff, users may be prompted to migrate the watch to the device they want as the main phone, but after that, Handoff itself does not make the watch switch back and forth. So for anyone expecting the Apple Watch to mirror the seamless phone-number handoff between two iPhones, it does not. The watch remains attached to one iPhone, and users may need to choose that pairing carefully based on which phone they rely on most.

3 articles · Updated · The Verge · Oct 15

Apple’s new iPhone Handoff lets one phone number stay available across two iPhones, with the active line shifting to whichever device the user unlocks.
T-Mobile is the first U.S. carrier to support the feature and will charge $5 monthly; Verizon plans support by year-end, while AT&T support has not been announced.
Apple positions Handoff for users who want a primary and secondary iPhone—such as a foldable Duo owner, a weekend phone user, or someone keeping a smaller iPhone.
The setup still looks niche: T-Mobile says the secondary iPhone cannot have other service attached and the feature does not work with T-Mobile business accounts at launch.