This works well if you are willing to do some basic wiring. I used it to control a space heater.
Sonoff TH16 WiFi Smart Temperature and Humidity Monitoring Switch for DIY Smart Home,Works with Alexa, Works with Google Assistant (With SI7021) https://www.amazon.com/dp/B07TC2KCGF/ref=cm_sw_r_apan_glt_fabc_9TX7PW0T85KQJN1GX82K?_encoding=UTF8&psc=1
I am using a Shelly H&T with the optional USB power supply. with it being in the freezer it has limited Wi-Fi range. without the USB power supply the battery would last about a week.
https://shelly.cloud/products/shelly-humidity-temperature-smart-home-automation-sensor/
my dad is using a Sonoff TH16 with Si7021 and a TH16 DS18B20
Amazon still has the TH16 with the SI7021 sensor available for immediate delivery.
https://www.amazon.com/Sonoff-Temperature-Monitoring-Compatible-Assistant/dp/B07TC2KCGF
Item | Current | Lowest | Reviews |
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Sonoff TH16 WiFi Smart Temperature and Humidity M… | $22.98 | $22.98 | 4.3/5.0 |
^Item Info | Bot Info | Trigger
Sonoff makes a $20 120VAC 10A Wifi switch that comes with a D18B20 temperature probe on a 1-meter cable. I bought one because I wanted a sensor on a cable so I would measure my water heater temperature. As a bonus, I also have the Wifi switch to control a device.
I installed Tasmota on it and it reports the temperature via MQTT every few seconds to HA.
https://www.amazon.com/Sonoff-Temperature-Monitoring-Assistant-DS18B20
Sonoff also has the $23 15-amp version that comes with a SI7021 non-waterproof temperature and humidity sensor on a 1 meter cable.
https://www.amazon.com/Sonoff-Temperature-Monitoring-Compatible-Assistant/dp/B07TC2KCGF