Like HowStuffWorks on Facebook!

How the Apple Watch Works

Apps on the Watch
Concentric rings show a quick view of the various physical metrics the Watch tracks.
Concentric rings show a quick view of the various physical metrics the Watch tracks.
© Justin Sullivan/Getty Images

The apps and their interfaces have been designed to allow for lighter interaction that works better on the smaller screen. Apple developed WatchKit to provide developers with APIs and other tools they need to develop apps for the Watch. Developers can already extend the functionality of their apps to create actionable notifications and Glances on the Watch. Sometime in 2015, Apple will allow third-party developers to create fully native Watch apps.

Several familiar iPhone apps have already been ported to the Apple Watch, including Calendar, Maps, Passbook, Music, Stocks, Weather and Photos.

Maps will open on your current location. You can move around the map via the touchscreen as usual, zoom in and out using the crown and touch the small arrow icon on the lower left of the screen to go back to your current location. If you do a force touch (press) on the screen, it will bring up Search and Contacts buttons that allow you to look for places and get directions. Search allows you to select Dictation or make a selection from Favorites or a list of recent searches. Once you've made a selection, it brings up information about the location and lets you choose walking or driving directions. The Taptic Engine gives you different feedback for each direction (left or right) when it's time for you to make a turn so that you could conceivably follow directions without looking at your watch.

The incorporated NFC will allow you to use the Passbook app not only for using loyalty cards or boarding planes and entering events with stored tickets, but also to store your payment methods and pay for things directly with the Watch at retailers that have touch payment capabilities. You do so by double pressing the button (underneath the crown) and holding the watch up to the retailer's payment reader. For safety, it doesn't store or transmit the actual debit and credit card numbers, but uses a specially created device account number for each card.

The Photos app shows your Favorites as tiny contiguous thumbnails on your Watch screen. You can zoom in using the Digital Crown, pan via the touchscreen or tap to further zoom in and swipe through individual pictures. Any photos that you mark as Favorite on your iPhone or Mac will show up on your Watch by default.

There are also two new health-related apps that use the capabilities of the Watch to help you manage your fitness goals. They're called Activity and Workout.

The Activity app monitors your activity throughout the day using the Watch's accelerometer and gyroscope to measure body movement, the heart rate sensor to gauge workout intensity and your phone's GPS and WiFi to track the distance you've moved. The information is displayed on an easy-to-glance-at graphic consisting of concentric rings labeled Move, Exercise and Stand. The Move ring shows calories burned. Exercise shows minutes of any activity comparable to a brisk walk or more. Stand shows the number of times you've stood up from a sitting position. You can click on each ring to get detailed information. The rings draw themselves throughout the day and close when you reach your goals. The app will even suggest new goals and give you a reminder to get up when you have been sitting too long.

The Workout app enables you pick an exercise from a list (mostly cardio workouts like running, walking or cycling) and set time, distance or calorie goals for that activity. You can see your progress throughout the workout and get a summary at the end. The app will also give you reminders when you've reached certain places in the workout, like the halfway point, and award you with badges for various achievements.

The Activity app works in conjunction with the Fitness app on your iPhone to peruse your activity and workout history. You can even share your activity data with third-party health and fitness apps through the iPhone Health app. The health and fitness capabilities of the Watch could make it a good, albeit expensive, alternative to the cheaper, less functional fitness bands such as the Fitbit and Nike Fuelband.

There are already some notable third-party apps in the works. Twitter will let you view and post tweets. American Airlines will allow you to check in and collect bags. City Mapper will purportedly give you directions for local mass transit and remind you of your stops. Pinterest will let you know when you're near sites you have pinned and give you directions. BMW can show you where you left your car and display your charge level. MLB will show you sports scores. Honeywell will let you remotely control your home thermostat from your Watch. Lutron will allow you to control lighting and "scenes" in your home. Nike can be used to challenge your friends to a run. Starwood Hotels even has an app in development that will let you to check in and unlock your room by waving the Watch instead of using a keycard. And many more apps for the Apple Watch are in the works.