The junction detector is a truly brilliant idea that, unfortunately, is probably rendered nearly useless now that everything in the world has embedded electronics in it.
Also, thinking about it, you could probably defeat the optical retroreflection detector by putting the camera behind a Faraday rotator (optical isolator). But those are quite expensive and you'd need to be really paranoid to use one, plus it'll only really work well if you match the wavelength of the laser.
Also, thinking about it, you could probably defeat the optical retroreflection detector by putting the camera behind a Faraday rotator (optical isolator). But those are quite expensive and you'd need to be really paranoid to use one, plus it'll only really work well if you match the wavelength of the laser.