> Density is really the critical variable, that's the first thing we measure. It's expressed as the number of people per square meter<p>I wonder to what degree this is detectable via computer vision? I would imagine most places already have some kind of CCTV on the crowd, so you should be able to retrofit a warning system into the existing security system (if there's any kind of standard, which might be a bold assumption).<p>Hopefully that could be done cheaply enough to make it reasonable to require them in venues prone to overcrowding, like smoke detectors.