“A friend in need is a friend indeed, a friend with weed is better” ~ Placebo

For me one of my favourites are my extractor fan control in my bathrooms. I have a switch on the fan and a humidity sensor close by. Turn on the shower and the extractor will turn on until the humidity is lowered enough, then switch off. In addition I have a static programmable button to press should you need it for other reasons. I just love the world of entities and how they link together to make something functional.