Continuity is one of the most important features in both iOS 8 and OS X Yosemite and one of the most important features in Continuity is call answering. Sure, Handoff is great, as is cross-compatible AirDrop, easy iPhone tethering, and keeping in touch with our green bubbled SMS/MMS friends and family. But being able to use your Mac and iPad as if they were iPhones? Being able to call Dr. Dre from your desktop? That's magic. And here's how it works!
Why voice calling matters
iPhones have full on cellular voice radios. That's what lets them make and receive calls over the traditional telephone network. iPads can optionally have cellular data radios, but that doesn't give them access to the telephone network. Macs haven't yet been given any cellular radios of any kind. iPads and Macs can both use Apple's FaceTime Audio service, or other voice-over-IP services like Skype, and that works great if you initiate or get a FaceTime or Skype call. But it doesn't help you at all if your iPhone rings and you're sitting across the room with your iPad or at your Mac.
Continuity's call making and answering does.
Other devices have tried transporting phone calls from phones to tablets or computers before, typically over Bluetooth and using a protocol that essentially handled the tablet or computer as if it were a wireless headset. It was the same technology, for good or for ill, that worked on a speakerphone system or in-car hands-free setup. Apple isn't using Bluetooth or mimicking a headset. Apple's using Wi-Fi and mimicking a telephone system.
As long as your iPhone is within Wi-Fi range, whether it's in your pants pocket, your bag across the room, or plugged in on the charger across the house, any phone call that comes in can be answered on your iPhone or iPad instead.
Call display, call answer, call defer
When your iPhone rings, Continuity can show you the name and number of whose calling on your iPad or Mac. It works just like the call display you're used to (provided you have call display service from your carrier and the identity information is available). Also, just like your iPhone, if the caller is in your contacts you'll see your contact picture for that caller, making them instantly recognizable even at a glance.
And just like on your iPhone, you can swipe the incoming call notification on your iPad, or click it on your Mac, to answer. Of course, if you're giving some big fancy keynote or are likewise busy and can't answer, you can choose to ignore the call, or even to respond with an iMessage or SMS message to let the caller know you'll get back to them ASAP. (Presumably, if you ignore the call on your iPad or Mac, it will get sent to voicemail, if available, on your iPhone.)
Call from contacts, calendar, or Safari
Making calls from your iPad or Mac is just as easy as receiving them. Any time you have a phone number in the built-in Contacts app, Calendar app, or Safari web browser, tapping or clicking on it will give you the option to call. Choose it and your call will be placed using the Wi-Fi connection to your iPhone, and your iPhone's connection to the telephone network.
Once a call is connected you'll see a time indicator — useful if you're counting local or long distance minutes — and you'll be told the call is "using your iPhone". Right below that is a sound wave just to add some visual flare.
You'll also get additional options, similar to what you get now on the iPhone. You can switch to a FaceTime video call, in which case the traditional telephone call is ended and the FaceTime call seamlessly connected in its place. You can also choose to mute the call so you can speak freely without the person on the other end hearing what you're saying, and end the call when you're done.
Apple hasn't shown off nor have they said whether Continuity calling will work with conference calls, though there was nothing in the demos that suggested an interface for handling them. However, starting off simply and adding functionality over time is a cornerstone of Apple's approach. The point being, this is a beginning, not an ending.
This fall millions of iPhones will ring and millions of people will be able to answer them on their iPads or Macs. Millions of people will also be able to place calls without reaching into their pockets, crossing the room to their bags, or sitting across the house tethered to their charging cable. If Continuity calling works as advertised — and we'll have to wait until the shipping version really gets hammered on to know for sure — then that's exactly the problem Apple will have solved.
If you've got an iPhone and an iPad or Mac, are you looking forward to making and taking calls on all your devices?