This method worked for other seniors I know. Set up his iPad with Face ID. Leave it plugged in at a table or other location where his face will automatically turn the iPad on. Set up your contact info - along with a picture - in his Contact list. Then instruct him to only answer if he sees your face.
A couple side items for his protection …
- Make sure you are the only in in his contact list.
- Then go into Settings > Phone > Silence Unknown Callers. This should block calls from anyone else.
Funny story … I set up something similar for my Dad a while ago. He loved it and it worked well … until it didn’t. Out of the blue, I’d get a call from him saying it was not working. I’d come over to discover that he had unplugged the unit and the battery died. I finally figured it was his way of saying he wanted more in-person visits. The more often I visited, the less often the “accidental unplugging” occurred. Never underestimate the power of a 90+ senior!