In my truck a warning light comes on when I go to take off if a passenger is sitting there but the seatbelt is not secured. After some research and thinking it may be their weight, capacitance or maybe an infrared beam (although I cannot see a sign of that). Maybe other things I haven't thought of?
I am a furniture manufacturer and would like to incorporate a night light into furniture to have a light come on at night automatically when someone stands up. The truck gave me the idea and I was thinking because they sell so many they have probably put a lot of thought into how they work. Does anyone know the solution the auto industry uses or have other good ideas on ways to go about it?