There is a Tizen SDK for wearables, downloadable from here by clicking the "Download" link on the top left. I try to create a "watch application" with the new project wizard, but I cannot run it inside the bundled emulator whatever I do. What I am doing wrong?
I have also tried the following beta version but all wearable options seem simply disabled (grayed) there.
Today I edited my answer before you posted this question. And I have mentioned that you can't test WatchFace applications.
There is a difference between WatchFace app and normal watch apps.
WatchFace app/widget are generally shown on the main screen of a smartwatch which generally consist of information like time/date and other small details.
A normal watch application can be any app like a game app, utility app etc. And it can be tested on emulator. I have developed many apps using Tizen SDK 2.3.1
So, its better if you ask your questions specific to the type of app, so that other people can answer it.
Now coming to your question about the usability of Tizen SDK 2.3.1. Yes, the SDK is usable for developing watch app and WatchFace app. But you can only test the watch app on the emulator not the WatchFace app.