I'm surprised that no one spoke about the AlertMe device from ResqMe, the same company that makes the famous emergency window breaker and seat belt cutter.
It kinds of (not the same level of monitoring) add the driver monitoring system to older vehicles.
Here is a direct link https://resqme.com/product/alertme/
I needed to sleep in a lit room without an eye mask on a cycling trip. What I did have with me was a neck tube (a.k.a. neck warmer/Buff). Folded over 3-4 times that was effect and comfortable, and stayed on better lying down than sleep masks. The advantage is that it forms a very wide band, spreading the load.
If I was buying one with that in mind I'd get ...