There are 2 ways for developing Gear applications : Gear Standalone, Gear Companion.
It consists of only Wearable-side Widget which
runs on Tizen-based Samsung Gear devices.
Develop enhanced standalone Gear app with enhanced network, call and Location-based APIs. Samsung Gear S can solely connect 3G network without mobile devices.
Try Magnetic, Ambient Light, Barometer, and UV Sensor APIs which are added newly as well as Accelerometer and Gyroscope APIs.
Create variety of notifications for Gear using Samsung Rich Notification SDK. Rich Notification SDK
Connect GALAXY device to Gear device, and send messages, data, and files using Samsung Accessory SDK. Accessory SDK
Tizen SDK for Wearable Samsung Accessory SDK
Getting Started with samples & Documents!
Secure your app to upload to Samsung Gear Apps