I'm quite fine with only malicious apps spying on me to begin with. I'm pretty sure Facebook or other large players wouldn't use that kind of trick.

Obviously that might not be enough for everyone, but it's by far the best solution that works with existing hardware. Tomorrows phones might have indicator LEDs or hardware switches, but my current one doesn't.

It’d be interesting to see if Apple added system UI on top of apps that tried to access the camera, displayed by SpringBoard so apps couldn’t draw over it.