Apple's new iPhone Handoff feature, launching with iOS 27, allows users to carry two iPhones with a single phone number by seamlessly switching between devices. The feature is currently available on T-Mobile in the U.S. and Telekom in Germany for $5 monthly, with Verizon and EE confirming support by year-end, enabling consumers to pair a foldable iPhone Duo with a high-end iPhone 18 Pro for optimal camera and screen capabilities.