It’s a Z wave controller. You have to plug it into a laptop to operate it. One of the competitors to SmartThings is the indigo system, which is software that you run on a laptop and then it uses the radio in the Aeon zstick to communicate with Z wave devices. There are other similar software systems that rely on the Z stick to provide the radio.
So essentially as a SmartThings user you already have the equivalent of the zstick inside the smartthings hub. You don’t need both.
It is possible to add a z stick as a secondary controller to SmartThings. Some community members have done that because SmartThings doesn’t give us any network mapping utilities at all. If you add a zstick as a secondary to your SmartThings network, you can then use the zensys mapping tools with Z stick and get a map of your SmartThings zwave network.
So it’s not likely that you would use the stick for any functional purpose with a SmartThings network, but you might use it for troubleshooting.
See the FAQ