In my experience (Tesla), attention monitoring works well even when I'm wearing sunglasses. The camera can still see my eyes even through dark polarised lenses.

It may depend on the sunglasses, however - other people report problems with sunglasses that have mirrored lenses etc.

I can answer this, since I have a new car with this camera and polarized sunglasses.

MOST of the time it's good about telling when I'm looking and when I'm not, out of maybe... 5 alerts over the previous 8 months all, but one occurred when I was in fact looking away for one reason or another. Likewise when it's correct my lane-keeping it's been right about me drifting.

Given how inattentive I see other drivers being, on their phones for example, and taking into account that I'm (based on my record) a good driver who is attentive... I appreciate these additions. I doubt that they make us less safe, we just dislike anyone or anything telling us how to drive, because "we already know what we're doing." The subjective experience of being distracted however isn't usually so clear-cut, it FEELS like you're paying attention.

Note: This is a new model Lexus, so I expect this represents that brand as well as Toyota, but beyond that I don't know.