Relevant: https://www.usenix.org/node/184422 "iSeeYou: Disabling the MacBook Webcam Indicator LED"

This doesn't work with recent MacBooks, only the older models.

But honestly, most people won't audit the wiring of their device. I wonder if a more low tech solution is the answer...a cover for cameras and some sort of sound blocking cover/plug for microphone holes.

That's the same argument that's been applied against open source software for decades now.

The reality is you don't need everyone to audit their devices, you only need there to be credible auditors. Better: standards mandates that require isolation of any ambient capture devices.

In the alternative, the ability to flood and overload such circuits might be of interest.

An ok from ifixit would be good enough.

I think that Jeff Bezos said this is how Alexa/Echo is built.

I can't verify by watching the clip now, but I believe it's in this interview: https://www.youtube.com/watch?v=yq0ecBGg5Q0

It's just after 5m45s : https://youtu.be/yq0ecBGg5Q0?t=5m45s

Apple's is in the firmware, but legend has it that it's possible to bypass.

It would be great to have the light show for both microphone and webcam access.

If it's in the firmware, it is possible to bypass. It must be a hardware switch to be credible.