It gets complicated. “The camera” is a bunch of parts. You’d probably want to key off of the CMOS sensor power, but that has several power levels for standby, sleep, idle. So your hardware circuit would likely to know current, not just voltage. Or maybe go upstream and parse the I2C (or whatever) messages signaling power mode changes?
And then your LED driver would need to know screen brightness (or connect to the ambient light sensor) because you want to be bright enough to see in direct sunlight, but that level of brightness would be unpleasant (and maybe screw up legit camera use) in low light.
So if you believe your SK is secure, you can do a better job more simply by using it. And if you don’t think SK is secure, all bets are off anyway.
And then your LED driver would need to know screen brightness (or connect to the ambient light sensor) because you want to be bright enough to see in direct sunlight, but that level of brightness would be unpleasant (and maybe screw up legit camera use) in low light.
So if you believe your SK is secure, you can do a better job more simply by using it. And if you don’t think SK is secure, all bets are off anyway.