According to a Rivian patent, it looks like Rivian is aiming to have a system where the vehicle can connect to electronic devices such as your phone, smart watch, fitibit or medical devices to get information about the driver's health and attention. For example, the vehicle could connect to your phone or tablet to see if you are watching a movie or texting or connect to your fitbit and see the driver's heart rate to determine if the driver is asleep or having a medical emergency (like a heart attack) and if so, pull over and call 911. Rivian's self-driving patent application hints at driver monitoring functionality I could see a lot of uses for this. Of course, it requires the driver to have one of these devices. Not everyone wears a fitbit or smart watch.
The recreational health monitoring are possible to realize in self-driving cars during the long commute. The continuous monitoring of vital signs, especially age-related ones such as hypertension, slow reaction times, and physical health changes can help drivers stay safe on the road.