There are many products that have been diligently tested by the SmartThings team and verified to work with SmartThings. You can find a list of these compatible devices here:
This list is not the last word in SmartThings-compatible devices, however. We’re constantly evaluating and adding new devices to grow the list. If you do not see the device you’re looking for, it may still be compatible with SmartThings but not listed because we have yet to test it to our complete satisfaction. To suggest a device for us to put through its paces, write in to support.
Alternatively, you can discover officially compatible devices from within the SmartThings or SmartThings Classic app. In the SmartThings app, tap on the Supported Devices card from the Dashboard and select a device category. In the SmartThings Classic app, visit Marketplace and select a device category under the Things menu. You will see which devices of that type work with SmartThings.