The magnet doesn't have to be that close, I reckon if for example you had a tunnel if you mounted one of those powerful little magnets on the entrance/exit you could use those to turn the lights on as they go into and come out of the tunnel... To a degree it all depends on where you mount the small circuit board.
Happily collecting things all my life...
(This post was last modified: 11-27-2021, 07:35 PM by Super.)