watchOS 2 has also been released today for Apple Watch. You must upgrade your iPhone to iOS 9 in order to upgrade your Apple Watch properly. New features in watchOS 2 include native Watch apps, meaning most or all app data is now stored on your Apple Watch, Nightstand Mode, and Time Travel, a feature where you can jump through different apps like your calendar right on your clock to see what’s coming up.
Don’t fear if your device can’t update to iOS 9 just yet, though. It usually takes a little while to push updates to all devices.
Update: It appears Apple won’t be pushing watchOS 2 today due to a major bug found in the OS. Until further notice, watchOS 2 is currently unavailable.
Update 2: Apple has fixed the bug in watchOS 2 and the update is now available for Apple Watch.