I worked on this feature for Apple Macbooks around 2014 as the security architect. All Macbooks since then have a camera indicator LED that is (barring the physical removal of the LED) always on at least 3 seconds. This feature is implemented in gates in the power management controller on the camera sub-board.

There's a LOT of pitfalls still (what if you manage to pull power from the entire camera sub-assembly?), this was a fun one to threat-model.