Mill Sense is a small device that measures and logs statistics on air quality, temperature and relative humidity. You will get an overview of the statistics in the Mill app. Mill Sense can use a built-in battery, which will last approximately 6 months, or it can be connected permanently to a USB power supply.
Mill Sens can also be used as an external temperature sensor for Mill Wi-Fi heaters and Wi-Fi sockets. This can be useful if a heater or socket is placed in a location that is colder than the rest of the room for example.