Along with a number of other improvements, iOS 9.1 brought enhanced Wi-Fi Calling support to Sprint in the U.S. While Sprint has supported Wi-Fi calling since iOS 8.3, now, Sprint customers can set up eligible secondary devices like their iPad, Apple Watch, and Mac to make and receive calls from their Sprint number over Wi-Fi.
"Customers already enjoy seamlessly responding to texts and email from a variety of great Apple devices," said David Owens, senior vice president, Product Development at Sprint. "Now they can bring that flexibility to the primary phone number their friends, family and colleagues know best. This great feature puts the power of device choice in our customers' hands."
In order to use Wi-Fi Calling on secondary devices, you must be signed in with the same Apple ID as you are on your iPhone. After you set up Wi-Fi Calling on your primary device, make sure to allow Calls from Other devies in the Phone section in Settings. On your secondary device head to Settings > FaceTime > Calls from iPhone to turn on Wi-Fi Calling on those products.