Ecobee 3. I'm new :)

Welcome to the forums! Ecobee is in “SmartThings Lab” status. That means SmartThings is working on an official integration, but it’s still in Beta.

http://www.smartthings.com/compatible-products/

Meanwhile @yvesracine is a community member who has contributed a lot of custom code to improve the integration. So there are people using Ecobee with SmartThings, but it’s not a completely smooth integration yet.

Before jumping over to the Ecobee topic, take a look at this for an overview of how custom code works with SmartThings:

And here are Yves’ topics on the Ecobee. The first is for basic functionality.

This one is specific to using the ecobee zone sensors: