There is a community washer/dryer in the garage of our fourplex. Unfortunately, the dryer is an older model and doesn't have a built-in humidity sensor to automatically shut off when the clothes are dry, and further, we cannot hear the buzzer from inside our apartment.

I would like to design a simple and cheap humidity and temperature sensor for the exhaust line. It should sense when the temperature and humidity of the exhaust reach levels indicating dryness and notify us inside. It should also notify us if the exhaust stops (rapid drop of temperature), indicating the timer has finished.