It's almost as if the vendors of common, must-have devices want to make it possible to spy on us. An enterprising journalist should ask why they don't make such switches. They certainly have deliberately made it hard for us to stop being spied upon -- even though we're their customers. Think about that. We're their bread and butter, and we're increasingly and rightly concerned about our security. Yet they keep selling us these insecure devices. That's just weird, isn't it? What the hell is going on?
I remember a loooong time ago when I was in high school, my mother's office got an Apple computer. On an IBM PC, the off-switch was an OFF switch, it stopped the power to the motherboard. On the Apple, it was a suggestion. You pushed the "off" button, and eventually the machine would get around to shutting off. Unless it was hung, in which case it would just sit there, forever. Mom solved the problem by unplugging it at the end of the day.
The answer is the same as it always is. Threat of bankruptcy. You spy, you die. That will take a social movement the size of the one currently being waged for #MeToo.
Update: Welcome Instapundit! In the comments, one person suggested an aluminum pot as a makeshift Faraday cage. Excellent thought!