not a big thing but I finally found a (relative) stable and cost efficient way of deploying various temperature sensors around the house.
Direct comparison with yr.no/Darksky Outdoor Temp. shows a big difference.
Thanks to @OttoWinter for esphomeyaml and the cheap prices on ebay for this setup:
Screenshot Group Card in the UI:
I use a cheap 18650 battery directly connected to the Wemos Lolin32 board. Voltage of the battery (connected to an ADC Pin), temperature and Humidity (DHT22) is reported every 30 minutes to MQTT Broker.
If the Voltage drops below a certain value shutdown is triggered by the the ESP itself.
Everything beside the actual sensor is inside and IP67 water and dustproof case.
The HASS package is just for the state card, the mqtt sensors and some templates and a notification automation if the battery is empty (persistent and pushbullet).
Let me know what you think or what I could improve.
lovelace config for sensors view:
Replaced the DHT22 with a BME280. Links and config changed. Old state card replaced by the lovelace config. Increased the deep sleep time to improve battery life.