I had a similar idea myself.
With the Scottish govt wanting every home to have smoke detectors, there are people on low income, that although own their home, can’t really find the money that’s needed to bring their properties up to the standard.
Neither can they afford to have simple repairs done, never mind a rewire or even fuseboard change.
I went to one the other day where their rather aged mains powered smoke detector had actually went on fire!
Took it down for nothing and left them a quote for a houseful of Aico.