With the power of Micropython it is easy to measure and monitor temperature in your hot tub, swimming pool, living room, garden house etc. The temperature is transfered with help of the MQTT protocol to the web site io.adafruit.com. You can monitor the temperature on Adafruits web page for free. Of course, you can use any other MQTT broker if you like.
The MCU is powered by a USB power bank. 2000mAh power bank works for several days becasue the script shuts down the MCU to deep sleep mode (battery saving) while not measuring and transfering.
The resistor should be connected between 3.3V and the data cable from the temperature sensor.
You will find more explanation in the micropython script.