For this one I used a pi5 running modified yolo to detect a hand. As long as the camera does not detect a hand it allows current to flow to whatever machine is running. Alternately, it could be used in line with an E-Stop to shut down a machine. 

Pi5 + Cam + YOLO => Relay => Machine power or safety systems

It went on to be the star of several patents in different forms. 

This project taught me more about business and manufacturing than any other. Basically, it is a vision systems control with real world outputs. Sometimes the outputs are startlingly fast, like single digit milisecond reaction times. It is an amazing learning curve on this one...I started with the CPU on a Pi5, then upgraded to the NPU on an Orange Pi5, and now I am running full tilt TPU on a Jetson Orin Nano. It is a work project, so I am not going to cover much here.