No this is not WIFI calling on the phone, that has been working for some time now.
This allows your other iDevices to make/receive phones calls using Sprint even when your iPhone is not nearby, or turned off. (Using your iCloud account).
It works fine, I shut my iPhone off, and then used Facetime to make a call to a landline phone. The displayed Caller ID was my cell number. I'm not really sure when you would need this, perhaps if your phone was lost or broken.
Apparently there will be a charge in the future to use this.
BTW I'm using the latest public betas for both iPhone and OS X.
oh hell yeah. I'm sorry i didn't realize that till later. i use that all the time. even if your phone goes to zero charge and you cant charge it, you can still place and receive calls on your apple watch, ipad, iPod, mac, that is why you want it.
that wifi calling feature when the iPhone is not nearby is not limited to FaceTime audio calls. they are wifi to cellular calls and i was testing it yesterday and "calls on other devices" work for text messages as well.
before iOS 9, continuity allowed you to answer a phone call on a mac or an ipad or whatever as long as your phone was on the same wifi network. so your phone had to be nearby and on the same wifi network. well now with iOS 9 , wifi calling , and "calls on other devices" you don't need it to be on the same wifi network.
so thats pretty awesome. so the special feature that t-moible currently has, is coming to sprint. now if only AT&T and verizon would allow it
you are perfectly fine on an unlimited calling plan, but if you are on a per minute plan, wifi to cellular calls deduct minutes from your plan, like using your phone on an legacy plan does now
this is the greatest thing in the world. its like having an AT&T 4G microcell at every free wifi hotspot for your ipad