[ArloL]

I believe Mercedes lane assist does this with via the steering wheel. They test whether you are actively driving. As soon as you take your hands off or don't move enough the system beeps after a few seconds to put your hands back.

[staunch]

Tesla does that as well but it's a poor proxy for determing if the user is paying attention. It would be much better to check if the driver is actually watching the road. The user that crashed into this firetruck was not watching the road which the Tesla could have easily recognized through eye tracking.

[kurtisc]

Tesla does it after three minutes. I can't think of any good reason an attentive driver would need their hands free for that long. It only takes a person thinking they can get away with checking their phone, or eating food, or looking around the footwells to result in deaths and, crucially, that person doesn't have to be the fatality.

[sschueller]

It is more complex than that. I analyses your corrections and compares it to its own data of the road. https://www.youtube.com/watch?v=A66zgJ4Oj8o