DHT11
Humidity and temperature sensor.
The temperature sensor is reasonably accurate but humidity is ludicrously inaccurate but can be used to determine humidity changes?
RPi
In the past (2/1/2016) the kernel mode for reading the DHT11 did not work reliably or at all but in 2024 it appears to be functional but may require a few retries.
config.txt
dtoverlay=dht11,gpiopin=17
Temperature
cat /sys/bus/iio/devices/iio:device0/in_temp_input 26000
Humidity
cat /sys/bus/iio/devices/iio:device0/in_humidityrelative_input 18000