Support for Multiple Apple Watches
When you upgrade from iOS 9.2 to iOS 9.3 and also upgrade to Apple Watch OS 2.2 you gain the ability to pair multiple Apple Watch devices to the same iPhone.
At this point it is not known exactly where this benefit falls into the scope of the average user. Rumors suggest Apple is working on the Apple Watch 2 for a Spring event, which could leave many users with two Apple Watch devices for at least a short period.
This feature requires iOS 9.3 and Watch OS 2.2, the later of which is not available as part of a preview program for regular users yet. Watch OS 2.2 requires iOS 9.3.