Car and Driver tested AEB in several vehicles (Tesla, Toyota, Subaru) and they are all pretty equally bad at it. Figuring out if matter in front of you, while traveling at speed, poses a life critical hazard is hard! It’s better than no AEB, but don’t rely on it entirely or you’re going to end up maimed or dead. As the driver, you are still the final responsible party.
https://twitter.com/vogon/status/1169358625220882432
Visual indicator after 2 minutes of no detected driver-applied torque to the steering wheel (apparently because they only detect torque - i.e. turning/steering motions - and not pressure?)
Since January 2018 there have been software updates that reduce the time that the car will allow you to not signal to it that you are paying attention. You now have to apply a little turning force to the wheel much more often than before.
The safety system is robust IMHO. If I push the accelerator pedal while autopilot is running, immediate nag. Running at 89 mph (max speed before Autopilot locks you out for the duration of the drive due to too high of a speed)? Nags every 5-10 seconds.
It’s not perfect by any means, but it also expects a responsible, aware driver behind the wheel.