Here is a project using Particle Core and SparkFun Gesture Sensor. This is s 3 in 1 sensor which detects Ambient Light and Color, Proximity detection and touchless gesture. SparkFun has created one Arduino library for this sensor which can be used on Particle Core with no modification (only one header files change).
This project use an Image Slider, which can slide left or right using touchless gestures. When you place your hand over the sensor and move right to left, the sensor will detect as LEFT gesture and the image slider will display next image. Similarly when you move from left to right, sensor will detect RIGHT gesture and image slider will display previous image.