My Mercedes E550 has it too, and it is used for drowsiness detection. The car suggests you should take a break if you look tired or like you will fall asleep. I have had warning to stop and take a break come on only once and I was indeed incredibly tired.
Wow, I rented a MB once and it did that, which was absolutely the right call. The thing was that I initially ignored it and thought MB used a timer or something but 15 minutes later, I became aware of it and it was quite acute by the time I was aware of it.
Do you have a source for this? My understanding is the Mercedes "Attention Assist" is based off driving behavior and not a camera pointed at the driver.
