The Leeo itself doesn’t show up as a device in the SmartThings app. On the other hand, it has its own app which will notify you on your phone, and that’s all some people need.
Alternatively, you can create a “virtual switch” which doesn’t exist in real life, but which SmartThings will treat like a real switch once you have created it. That means it shows up on your list of things, you can toggle it on and off with the SmartThings mobile app, you can have smartThings routines turn it on and off, etc.
Then you would use the free IFTTT service to automatically turn on the virtual switch whenever the Leeo hears a target sound. That way you have something in your SmartThings account which goes on when Leeo hears something. 
IFTTT stands for “If This, than that.” It’s a free service that is used to create integration between different products/services that don’t normally talk to each other. In this case, you would use the Leeo as the “if” and SmartThings as the “that.” So you just set up a simple rule in IFTTT so that if the Leeo detects a particular sound, then smartthings turns on the virtual switch.
https://support.smartthings.com/hc/en-us/articles/211978466-IFTTT