The second beta of the forthcoming iOS 9.2 software update delivers additional fixes and enhancements for the Apple Watch, Audio, Networking and Safari, while enabling AT&T Wi-Fi Calling on the Mac.
To apply an over-the-air update to your iOS device, go to Settings → General → Software Update and follow the onscreen instructions. You can apply for Apple’s Beta Software Program here to gain access to public beats of iOS and OS X.
As detailed earlier this morning, iOS 9.2 beta 2 expands the usefulness of Wi-Fi Calling with support for AT&T’s network-level technology called NumberSync which lets you place and receive phone calls from your Mac running OS X 10.11.2 beta 2, even if your iPhone is turned off.
Wi-Fi Calling screenshot via 9to5Mac.