A key feature that makes the iOS 8/Yosemite combination so powerful is Handoff, a scheme that lets you transfer tasks from one device to another. This lets you start working on something in one device, and then smoothly and seamlessly take up the same task on another--start on an iPhone and then move to your Mac, for example. iOS 8 already let you use Handoff between an iPhone and an iPad, but now with the launch of Yosemite, your Mac can get in on the fun too.
Before we examine each of its elements, let's be sure that you can actually use Handoff. To take advantage of Handoff you need a MacBook Air, MacBook Pro, iMac, or Mac mini made in 2012 or later. The late 2013 Mac Pro is compatible too. Your Mac must be running OS X Yosemite and you must have iOS 8 on your iPhone, iPad, or iPod touch.
Devices should be within approximately 33 feet of each other. And any devices that you wish to use with Handoff must be signed into iCloud using the same Apple ID. Additionally, you must switch on Bluetooth for these devices to talk to one another via Handoff.
To enable Handoff on your Mac, launch System Preferences, select the General preference, and enable the Allow Handoff between this Mac and your iCloud devices option. On an iOS device you instead go to Settings > General > Handoff & Suggested Apps and then switch on Handoff.
Now that you've configured your compatible devices correctly, let's see how Handoff works.
Handoff and apps
The idea behind Handoff and apps is that you can launch an app on one device and then, when you're in range of another, continue your work on that other device. For example, you might be working on a long note on your iPhone and, walking into your home office, choose to finish your work within your Mac's version of Notes. Likewise, you can hand off apps between iOS devices--start work on an iPod touch and then hand it off to your iPad.
Currently compatible apps include the iOS 8 and Yosemite versions of Calendar, Contacts, Mail, Maps, Messages, Notes, iPhone, Reminders, and Safari. On a Mac running Yosemite, Keynote 6.5, Numbers 3.5, and Pages 5.5 are compatible as are version 2.5 of Keynote, Numbers, and Pages running under iOS 8. Third-party apps can be written to take advantage of Handoff as well.
Handoff on the Mac
To use Handoff between an iOS device and a Mac, simply launch a compatible app on your iOS device. When you do, a Handoff icon will appear at the left of the Mac's dock (or at the top of it if you've pinned your dock to one of the sides of your display). To use the app on your Mac, just click on this icon and the app will launch and display the content that you were viewing on your iOS device--a Safari webpage or map, for example.
Alternatively, you can press Command-Tab to bring up the Mac's application switcher. If an app can be handed off, you'll see its icon to the left of the switcher. Select it and the appropriate app will launch.
Handoff on an iOS device
On an iOS device you'll see evidence of Handoff on the lock screen. When an app is available for handing off, you'll find its icon in the bottom-left corner of the screen. Swipe up on it, enter your passcode, and the appropriate app will launch on your device and display its current content.
You needn't quickly lock and unlock your device just to access Handoff, however. You can also double-click the Home button to get to the multitasking screen and swipe to the right. The first pane you see in this screen is used by Handoff (see the image at the top of this page). Tap it and the correct app will launch.
In either case you can continue to work within an app and then hand it back simply by invoking Handoff on the original device. Or, if you like, hand it off to yet another compatible device within range that shares your iCloud address.
Note that the device you're handing off from must be awake and unlocked. If, for example, you're working on an email message on your iPhone and that iPhone automatically locks, Handoff won't work until you wake the phone and unlock it.
And that's Handoff in a nutshell--a convenient way to get your work done from whatever device is best for the job.