[wadetandy]

It seems to me that if an attacker can get access to your microphone and camera, you have way bigger problems and they don't need your PIN at all.

[jpindar]

So never install any apps that use the camera and microphone? Putting your finger over the camera when entering a PIN seems more practical.

[wadetandy]

But these apps shouldn't be running/accessing those devices when your phone is locked. If the apps can manage to get around that permissioning issue then they can control a lot of things directly, most likely, and don't need your PIN for much.