It should come as no surprise that wearable devices are naturally superior to handheld devices in their capacity to deliver notifications to the user. With a handheld device, you hear a beep, and you need to draw your device out from your purse or pocket or whatever choice holster you snagged at that recent eBay auction.

But with a smartwatch, things are quite different. When you hear that beep, you simply glance at your wrist. This ease is a hallmark feature of wearable device technology.

And it doesn't end there. With the help of voice interactions, the user can act on that notification by issuing a recognizable voice command. The voice interactions API, of course, predates the Wear API and has been in use on handheld devices for some time. But there is no denying the immense value it brings to wearable devices, fitting in perfectly with that ease of access. We'll deal with voice interactions in the next chapter.

So central is the notification model to wearable devices that...