When I was a kid I enjoyed putting together a scary scene at the top of my parents driveway complete with lights and sound. This year i decided to put together another scene using many of the old props from when I was a kid. I had a fog machine that had a manual control and required you to stand next to it and press. Very inconvenient when your trying to put on a scary scene. So I modified the controller so that it can be controlled from an Arduino connected to an Android app. I also have added motion detection so that it can control itself whenever someone walks up the driveway but decided to use the app primarily.
I did one myself with a NW.js React app and Arduino Ethernet shield: https://github.com/jim-blog/fog-machine