mmWave sensors are a recent sensation in the Home Assistant community. Unlike passive infrared sensors, which detect motion, mmWave sensors detect the presence of objects by emitting high-frequency electromagnetic waves in the millimeter wave band. These waves are reflected by any objects in their path, and the sensor then analyzes them to determine the distance of the object. Thus, a mmWave sensor will pick up your presence when you are sitting on a chair and working for hours, or watching TV on the couch while barely stretching a leg.
Currently, most mmWave sensors on the market share a common drawback – they are relatively expensive. This is especially true when compared to the more widely available passive infrared sensors. However, as production of mmWave sensors increases, costs are becoming more reasonable. In the upcoming Home Assistant Core 2023.2 update, support will be added for the Hi-Link LD2410B, which at ~US$4 is one of the most affordable options available. Though it may be a bare board without a casing, it does support Bluetooth Low Energy, and it can be easily discovered by Home Assistant and its Bluetooth proxies.
