My son Erin is designing the electronic components of Professor Tauruscat's helmet, and has included an ultrasonic range finder as a switch for the lights. I am mounting this on the front of the helmet. It works by sending out an ultrasonic beam that measures how far away the object in front of it is. Depending on the distance it signals the Arduino to perform a certain sequence of lighting the LEDs.
The URF is shown above at the bottom center, and will be press fit into the acrylic mount on the right, than inserted into the leather plate that is shown being stitched together.
I constructed the mount to incorporate the URF into a Victorian looking plate so that it would not look out of place. The leather and mount still need to be antiqued.
The URF switch will allow me to wave my hand in front of the helmet and activate the blinking lights.