Mark Gurman, Bloomberg:

Apple Inc.’s HomePod mini speaker launched last November with new features such as a home intercom system. But one part of the device has remained secret: a sensor that measures temperature and humidity.

And:

The Cupertino, California-based technology giant never disclosed this component and the device currently lacks consumer-facing features that use it. The company has internally discussed using the sensor to determine a room’s temperature and humidity so internet-connected thermostats can adjust different parts of a home based on current conditions, according to people familiar with the situation. The hardware could also let the HomePod mini automatically trigger other actions, say turning a fan on or off, depending on the temperature.

And:

The part is situated relatively far from the device’s main internal components, meaning it is designed to measure the external environment rather than the temperature of the speaker’s other electronics. Many mobile devices include sensors that can trigger the device to slow performance or disable features to stop components overheating.

Is the sensor for internal use only (monitoring/adjusting to environmental conditions)? As in, nothing to see here, just some normal design, folks.

Or is there, as Mark hints, a stealth opportunity to link to HomeKit in some future iteration?

Very interesting read. No clear answer.