I have several animatronic figures I use outdoors for Halloween. They riun on Esp8266 microcontrollers and have mp3 players, addressable leds, and std cheap pir motion sensors and they work pretty well now. I thought I would try to upgrade to some sort of gesture detection for next year. I'd like to try to detect kids waving at the props, of course disregarding other motion. I've done preliminary testing with digital lux sensors and ultrasonics, and so far the results aren't good enough. With signal processing I thought I could detect waving motion in a sensor signal. That's like a frequency of 2-4 Hz (cycle = back and forth). Do you think there is a way to do this without resorting to machine vision? The number and type of sensors available is bewildering. This should be easy, right?