Another economic inverse-function line of business (see the full post for context-setting)
The basic idea behind this new wrinkle in surveillance is that cameras bolted to walls, embedded in ceilings, and posted on light poles don't really do much. When they're monitored 24-7 by a human, that's expensive - and it's very easy for the person watching to get sensory overload and miss important events. When they're not monitored, all they're doing is recording crimes for later analysis: Let's see if we can identify who that hooded guy was who stole your car last Friday night.
But take high-resolution digital cameras, slather on some software to analyze the images they're capturing, add loudspeakers (more on that in a minute), and connect them to zippy data networks, and they can be monitored by off-site personnel, only when something unusual happens.