My little ESP8266-based humidifier.

It has an attached DHT22 temperature/humidity sensor and a 5V relay.

The principal variable is a struct, settings, containing the following:

• humidityLowerBound (float) - Humidity level at which the relay should be turned ON.
• humidityUpperBound (float) - Humidity level at which the relay should be turned OFF.

It has the following HTTP API.

• GET / - JSON output of all current data.
• GET /humidity - humidity (float)
• GET /temperature - temperature (Fahrenheit) (float)
• GET /settings/humidityLowerBound - humidity lower bound (float)
• GET /settings/humidityUpperBound - humidity upper bound (float)
• POST /settings/humidityLowerBound - set humidity lower bound (float), using the value parameter
• POST /settings/humidityUpperBound - set humidity upper bound (float), using the value parameter

It allows OTA updates.