I find it interesting that people's main concerns are the privacy laws. Isn't anyone concerned that there is a need for gunshot detection? I would have thought that the main issue was that there was enough gun related violence to make this product viable? As much as I love to see an innovative solution to a problem this seems a lot like its treating the symptoms and not the cause.
Won't somebody think of the children? The problem is that there's always a good justification for reducing rights. It makes law enforcement easier. We need to fight terrorism. We need to stop child rape. Etc, etc, etc. But if you let your rights be stripped away, even for a purportedly good reason, you aren't getting them back.