Quantity   Component name
3 × (Arduino Pro Micro) Temperature and humidity loggers. (Replaced by ESP8266)
3 × (HC-06) Bluetooth connection from Arduino to local Node.js forwarder. (Replaced by ESP8266)
3 × DHT22 Temperature/humidity sensor, one per each floor of the house
2 × DS18B20 Temperature sensors for measuring the central heating water temperatures
2 × ESP8266-01 WiFi temperature and humidity logger using MQTT.
1 × NodeMCU 1.0 WiFi temperature and humidity logger using MQTT. More pins, more sensors.