[finnw]

And maybe predict domestic violence before it happens.

I'm not sure if I qualify as one of the "privacy folk" or not, but I would say "As long as the police cannot compel you to install the thing and switch it on, or have an AI system issue search warrants in seconds based on what the machine reports." Unfortunately I think we will have both of those things 20 years from now.

[danbruc]

There is no need to force anybody to install and turn on anything - they could just passively monitor the signal of your wireless router, our that of your neighbor or of your cellphone. Or they could actively send such a signal and analyze it if they don't care about being detected. In the end it is some kind of (passive) radar and you will probably have to actively jam or block it in order to prevent someone from monitoring you.

[jerf]

An AI system issuing warrants defeats the entire purpose of warrants. The entire purpose is to put human oversight into the system.

Whether you consider this a fatal objection to the idea or a problem to be solved is an exercise for the reader. (The future is weird.)