Fire service offer a free smoke alarm service to vulnerable people, but they
glue them to the ceilings and I'd expect that is not very secure either.

Not a bit of it!
The Fire Brigade fitted two of them here and glued them to the ceiling
paper with No More Nails (or something similar)
They were Fire Angel alarms, a little larger than most, and have a
back-plate to which the alarm can be fitted or removed with a twist.

In due course, the downstairs one went faulty, and when I tried to
remove it from the plate it wouldn't budge. The whole thing was glued
together. I used a serrated knife to saw through the glue, but it cut
a hole in the ceiling paper. I bought a similar Fire Angel to replace
it so the hole is hidden.
--

Graham.
%Profound_observation%