I had a "smart" smoke detector that's older than nest. It would connect to other smoke detectors, and tell you "there is a fire in the garage". Or any other roo

I had a "smart" smoke detector that's older than nest. It would connect to other smoke detectors, and tell you "there is a fire in the garage". Or any other room or building. Which you wouldn't get from a regular smoke detector. It's not really for residential use, but there are definitely use cases for remote smoke detectors.