The Apple Watch is, first and foremost, an iPhone accessory. It might be even more than that eventually, a truly independent gadget, but a vast majority of its current functions like making calls, sending messages, getting information, even playing any third-party games.
Apple has several timer and clock apps apart from the stylized watch faces, which also work when your iPhone is disconnected and offline. You can use Apple Watch like a full-featured chronograph and watch, or as an alarm clock. And of course, you can use Apple's own beautiful watch faces, too, which will still tell time.
Most functions require your iPhone to be on, have Internet service, and be paired with the Watch via Bluetooth or a shared Wi-Fi network. If you're thinking about getting one, make sure you know that. It requires an iPhone 5 or later, and it can't even be set up without one. All third-party apps (those not created by Apple) need an iPhone connection to work.
The Apple Watch can do a quite a few things without your iPhone around:
2GB can be used to store music. You sync music with Apple Watch via your iPhone and the Apple Watch app, no Mac or iTunes required. Once your music is synced, you're free to listen as long you have a pair of Bluetooth headphones.
Apple has two built-in fitness apps called Activity and Workout, and both work away from the iPhone. You can measure heart rate, too. Activity tracks steps, time spent standing, and active exercise. Workout allows timed exercise sessions that measure pace, distance, heart rate, and calorie burn estimates for various activities. The only thing you can't do away from your iPhone is track your walk or run with GPS.
Once you set up a credit card for Apple Pay to work on Apple Watch, it keeps working even when your iPhone is not attached.
You can store boarding passes, tickets and gift cards in Passbook in the form of QR codes, and it's a great alternative to Apple Pay for a lot of stores and services.
There's a small photo album app on the Apple Watch that stores up to 500 photos from your phone library or iCloud.
Reading messages, recent calls and even offline voice mails
You can't make phone calls away from your phone, Reading messages, recent calls and even offline voice mails but you can see who's called recently, and read already-sent texts. Surprisingly, you can even listen to voice mails! You won't be able to receive new messages without connecting your phone again, but at least you can browse missed connections.