In our house, the home theater room shares a wall with the master bedroom. Instead of trying to remember to turn the subwoofer on/off, I decided to use a zigbee controlled outlet to control the power supply for the subwoofer. This way I can control it using either my SmartThings app or my Alexa (via SmartThings.) I leave my subwoofer power switch in the “auto” position, but this way I don’t have someone banging on the wall late at night because of the “boom boom” sounds.
I used a Peanut controller. They are rated to 12A. I know it is not directly supported by SmartThings, but they are cheap, and will function as a Zigbee repeater. If you can find one with the most current firmware update, then they work well, and also report power consumption correctly. If you watch for them on sale, you can find them as cheap as $10 apiece.
I did not write a device handler for this device. The custom device handler I found works perfectly without any modifications. I will give kudos to the person who did write it. You can find it here: https://github.com/pakmanwg/smartthings-peanut-plug/blob/master/deviceHandler
It’s easy to pair. Just start the “add device” function on your app, and then plug the device in to power.