Continuity was introduced back on iOS 8, the feature allows you to accept phone calls on your Mac or iPad if you ever leave your iPhone some where in the house or office while its connected to the network, Apple has improved the functionality in iOS 9, despite not being made as a major announcement in WWDC 2015, Continuity now works remotely over Cellular networks, which means you don’t need to have your iPhone with you and still able to receive phone calls with your Mac or iPad wherever you go.
As reported by 9to5Mac, this feature was found in the first beta of iOS 9 and U.S carrier T–Mobile is the first to work closely together with Apple to make this feature happen. In order to make this feature work, you’ll need to ensure that all of your Apple devices are linked to the same Apple ID, and all devices are connected to an internet enabled WiFi network. The difference between the current feature is that you don’t need to be connected to the same WiFi network in order to enjoy cellular Continuity, and we certainly believe that you will be able to use cellular data to transmit voice remotely to other devices in the near future, FaceTime video calls did went through the similar approach last time.
Should your cellular network support it in the near future, the feature can be found in Phone settings in which Apple will allow you to choose receiving phone calls from a list of devices that is connected to the same Apple ID, this is going to be useful for forgetful folks who usually leave their phones at home.