Originally Posted by
gfunkdave
Yeah, the feature was introduced on iOS 8. Your phone communicates via the local wifi network with other devices signed into the same Apple account on the local network. It's the same way I can make regular phone calls on my iPad - it goes over wifi to my phone.
Thank you for explaining this ^ (and I figured it was something like that) as a few weeks back, I called goalie-parents at their place in Palm Beach on goalie-mom's iPhone and she answered the call on her iPad as both her iPhone & iPad (wifi only) were both connected to their wifi network