Amazon has done a really nice job with that last one, offering up a sensitive dimmer switch with 24 notches, and a reminder to use a high setting for brightly lit rooms and a low setting for dark rooms, as unintuitive as that might sound.
Scientists have used chromophores for decades to detect chemicals, but, until Fido, they weren't sensitive enough to detect trace explosives because each molecule of TNT vapor would switch off just a single chromophore, with the result that faint wisps of evil chemicals caused no visible change in luminosity.