The rich don't like negative interest rates, are pulling cash out of Swiss banks

So there are more hoards of cash in the world! Cool! I bet part of why rich peeps feel like this is realistically doable now is because of technology. They have a Nest or something and a smartphone and because they can access cameras at their house anytime they feel like they are more secure.

But what could happen is that an enterprising h4x0r (possibly one who works for one of these IoT companies) realizes that even better than peaking at dick picks, you could have a comprehensive catalog of who is keeping this cash and where. You could then either sell the data (cheap at first, expensive later) or act on it yourself.

My point is that if you're loaded and hiding cash on-site, you probably don't want a normal commercial IoT system. You probably want something built for you by the suitably paranoid people on websites like this one! (I suppose that's another security risk, though.)

who would have guessed people don't like it when their money evaporates

It is darkly amusing that the actions of the wealthy are indirectly causing negative interest rates. Wealth, like fertilizer, needs to be spread around to do its magic. The only known robust solution to this problem is to invest in the general public and only governments are sufficiently large and broad to be able to do that. Neoliberalism is turning out to be yet another economic framework that is simple, neat, and wrong.