> Can you imagine other use cases than projection?

yes

vtubers

human interface device for quadriplegics

automated camera tracking/zoom for video calls

emotion recognition support software for people with difficulty reading or understanding emotions (ASD)

truly smart, smart home that can track and respond to gaze, e.g. "can you turn off that light" and it will turn off the light they're looking at

sleep detection for smart locks

liveness detection for identify verification systems

vr tracking for interactions that both escape the uncanny valley, and feel more real time

need more?