The sensor works best indoors between 15 and 30 degrees Celsius (59 to 86 Fahrenheit) and when humidity is between 30% and 70%, Apple says on its website.

You don't need to use Eve Degree with Apple's HomeKit, but it's how you make the most of the $69.95 sensor. On its own, it'll show temperature or humidity – you switch between with the button on ...

The sensor is made by Texas Instruments, which calls it a "HDC2010 Humidity and Temperature Digital Sensor," according to TechInsights, a firm that analyses components inside of electronics.