but there were obviously going to be either a number of false positives or negatives that make it less valuable as such.
It really comes down to the specifics of the technology and how it's implemented. The system I worked on was astonishingly good. Even the local police of a particular installment wanted to do a test of the system (basically walk around with various guns of all different sizes) and they were stunned at how well it worked.
The funny thing was that we built the system to work 100% locally, and we even insisted on air-gapped networks (but wasn't a requirement). The amount of people and companies who asked if we could connect the system to the internet for easier access was worrying. Whenever we tried to explain the basics of data security and the potential issues we were just looked at like we were nuts.