In addition to the major iOS 9.3 software update for the iPhone, iPod touch and iPad, a companion software update for the Apple Watch released this morning, too. The new watchOS 2.2 firmware is now available as an over-the-air download in the companion Watch app for the iPhone.
watchOS 2.2 is not as major a release as iOS 9.3 or OS X 10.11.4 so ti includes only a few improvements such as the Nearby feature in Apple's Maps app, the ability to pair multiple watches to a single iPhone and more.