The Nexus 9 isn't the only device getting a 5.1 update today—Motorola has made the Android 5.1 update for the 2nd gen Moto X official and has started sending it out. The rollout is starting with a soak test in Brazil, but it shouldn't be long before it hits all the Moto X variants.
Motorola didn't go into detail about when the update (version 23.11.14) will reach carrier versions of the phone, but the changelogs from yesterday listed both unlocked and AT&T versions of the phone. The unlocked Pure Edition will probably be the first to get the update in most markets.
You can check out the full changelogs for all the details, but Motorola called special attention to the new chop-chop Moto Actions gesture to activate the flashlight. There are also the various tweaks and fixes that come with all Android 5.1 builds.
Motorola has only now gotten around to pushing out the final update.