I dont have an apple watch but looking on the app store it looks like there are two apps. SeizAlarm: Seizure Detection. and Overwatch Seizure Detection.
I dont use apple products so I cant tell you anything about them.

My mother had the same problem that you are going through. We lived in a small house so she started just sleeping with one eye open. Thank you for caring about your son so much.

The seize alert app is pretty effective. However it does drain the charge on the watch pretty fast. So 8 hours is the max so keeping track of the battery is key. My son had a seizure and the watch was not charged or ran out so it couldnt alert us. Hes more aware that this is essential to having more freedom as hes 18. We do like to test ot once a week to make sure the settings are good. You can ajust higher or lower sensitivity.

How is the seize alert app working out?

I also have the SeizAlarm app but luckily I haven't had to give it a real world test since I got it.

We use seize alert app with Apple Watch