WhatsApp was surprisingly quick off the draw after the release of Android Wear, updating its sideloaded beta app with Wear support early this month. Now the 2.11.362 update is available on the general play store release, so even users who don't want to use the beta (or who don't know about it) can get richer WhatsApp chat notifications on their wrists. Huzzah!
The update to the main app includes most of the standard Wear messaging stuff: full long message viewing, nested/stacked messages with sliding navigation between them, and the usual reply via voice option. Incoming messages can be dismissed with a swipe, just like pretty much all Android Wear notifications. The update also includes the usual bug fixes and "improved message storage reliability," but no other significant changes to the unlimited messaging app.
WhatsApp is a free download for Android 2.1 or higher. Full access to the chat platform costs $1 per year.