Horror movies are the best source of inspiration when it comes to XR projects.
An engineer from Twitter made a simple but unexpectedly creepy AR app. If a user turns off the light, there is something hidden in the dark.
The developer used the ability of devices to detect illumination. If a device detects darkness, the AR app turns on additional content. This awesome project was developed with ARKit in Unity.
The idea is based on a horror movie called Lights Out (2016). The developer noted that horror movies can be of great help if you are looking for inspiration.