[nbutyllithium]

It's specifically enabled for those enrolled in the full self driving beta (and only while it's enabled). As far as I know it's not yet made its way to those who just use autopilot which is what was used with that remarkably dangerous backseat stupidity.

Edit: Zaroth's comment makes it sound like it's now enabled for normal autopilot use as well https://news.ycombinator.com/item?id=29598520

[zaroth]

I am in the FSD Beta queue but I have not gotten access to it yet!

I wonder if the more aggressive monitoring and alerts turn on when you enter the queue for FSD Beta as a way to monitor your alertness before granting entry into the Beta?!