I didn't know they existed, that's horrible. You get automatically scanned when driving throughout cities in the US, in case you are a criminal?
I'm surprised this exists, but I'm very surprised that people aren't furious about this (AFAIK) especially in the US of all places.
Since when was checking if a random person is a criminal acceptable behaviour in a free society? If the authorities have reason to suspect you have committed a crime then I can understand it but to just check everyone all the time is ghastly.