Important distinction. If your microphone is compromised, your web cam might be triggered to turn on just long enough to take a photo, or the camera could turn on only when the mic is quiet and there are indications the person is not engaged with the computer.
Note that this is not only about security. Sometimes a user simply makes a mistake, or have an app configured the wrong way, and accidentally turn on their cameras without intending to. Nothing has been compromised, everything is secure, but they still suffered an unexpected exposure. A camera cover will prevent many of these situations.
Should be a tiny mechanical device in addition to the light and it should only unlock with touch id. Same for microphone. Honestly, I want the same thing for phones too. The ease by which we are monitored is too damn high.
Yeah, light can turn on when one is looking away from the computer or sleeping and could potentially be spied on. A cover is a non spying guarantee, at least the visual part, spies can listen on the mic though
A camera cover guarantees that the camera can only work when the camera is uncovered.
A camera light alerts you once the camera is already on.