Apple’s new Secure Indicator Light (SIL) mechanism. When using the microphone or camera, the corresponding indicator dot is effectively rendered in hardware, making it a lot less likely that any malware or user space app would be able to access those sensors without the user’s knowledge.
If this mechanism isn't working as intended, Apple pays $100,000 to $2,000,000 bounty for bugs that breach security boundaries which protect sensitive user data or sandboxes.
That's cool but someone needs to find said bugs and Apple is not exactly open for audit. Given the critical nature of smartphones, I think corps of this magnitude should be subject to oversight and clear and transparent external evaluation of such sensitive systems.
https://security.apple.com/bounty/categories/