Best bed alarm.

I went to google and typed "best bed alarm for elderly" several came up and sold on Amazon. Depending on your need is what you need to look for.
Also, buy a kids bed rail - about $40.00
I purchased one of those concave mattresses and that worked well with my daddy.
Some nursing homes do not allow guard rails but it does not state about kids bed rails!
Blessings

Putting the mattress on the floor so they can't get out of bed unsafely in the first place. Or, a concave mattress.