Handoff—a feature that allows you to quickly move between devices and pickup right where you left off—first appeared with iOS 8 and OS X Yosemite. It allowed you to seamlessly move between an iPhone and an iPad, and iPhone and a Mac, Mac and an iPad, etc.
Unsurprisingly, Handoff is now available on the small screen with Apple Watch. It will allow you to do things like check email on Apple Watch, and seamlessly switch to your iPhone to has out a reply. Have a look at our tutorial inside for a walkthrough on how it works.