Apple WatchOS 2 adds new faces, new functions, and more opportunities for app developers

At its Worldwide Developer's Conference, Apple announced its upcoming Watch interface, WatchOS 2, which cracks open many core device features to third-party developers while adding new features and making the Watches more independent of the iPhones that synchronize with them. There will be more customizable watch faces with intriguing effects, a Friends list that can expand beyond the current 12-contact limit, and new freedom for native apps to tap into the Watches' on-board processors and sensors. (The company also announced a music streaming service and updates to its desktop and mobile operating systems.) Here's a brief look at some of the new things you'll be able to do with an Apple Watch when WatchOS 2 debuts to consumers in the fall—software developers can get a version now.

Going native. Many apps, including those from third-part developers, will be able to run on the Watch without checking back with an iPhone. Fitness apps will now work on the Watch, even without connection to an iPhone, and Siri will be able to handle many functions, including initiating an exercise routine. Apple says this will help apps load faster and offer more features.

Third-party developers will, for the first time, have access to the Watch's Taptic engine, Digital Crown, accelerometer heart-rate sensor, and even video capabilities (details to come).

There's also a home-control option for Insteon products.

New face, new tricks. Apple will put a friendlier face on its Watch interface: your friendlier face. You'll be able to supplant a boring watch-face background with a personal pic or an entire photo album. If you choose an album, you'll be greeted by a new face every time you tilt your wrist up to view the Watch. Apple will initially offer some interesting prerecorded time-lapse-photography scenes from around the world, such as a London sunrise to sunset, and you'll eventually be able to create your own. Also, third-party developers will be able add their own elements to the Watch's face.

One click forward, two clicks back. WatchOS 2's Time Travel feature will let you scroll forward or backward in your schedule, including the weather and headlines for that day, by rotating the crown. (Some users will no doubt be disappointed that the Watch won't show you future headlines.)

Looking for a high-tech timepiece? Check our smartwatch buying guide and Ratings.

Good night. Apple found a new use for your Watch while you're charging it at night. Nightstand mode lets the Watch act as a bedside alarm clock showing you the time and date, and waking you up with an alarm. Just tap the Watch crown if you want to keep snoozing.

The more, the merrier. While the current Watch OS limits your circle of friends to 12, WatchOS 2 will let you maintain several pages of frequent contacts. You can add contacts from the Watch, and also rearrange them on your iPhone's larger screen.

Apple Pay expands. Apple Pay, which can be accessed through the Watch, will reach beyond credit cards with the addition of store cards from JC Penney, Kohls, and BJs. Rewards cards, including Walgreens', will also be added. And, for the first time, Apple Pay will be accepted outside the US. First stop: 250,000 locations in the U.K., including mass transit. Also, Apple says it will coordinate with Square, which makes widely accepted portable credit-card scanners, to make Pay available at more retailers.

More reply options. WatchOS 2 will now let your reply to FaceTime calls (audio only) and e-mails.

A better way to travel. In addition to driving directions, iOS 9 will let you plan a trip using a variety of transportation forms (foot, bus, train). The Watch will also show you more details of such trips, including transportations schedules and estimated times of arrival.

We'll have more on WatchOS 2 in the coming weeks. Stay tuned.

—Mike Gikas