Xiaomi Motion Sensor
A motion sensor that works with the Xiaomi Gateway.
This works very well with Home Assistant once it is set up. Worked better (with lower latency) than the other, more expensive devices I tried.
Home Assistant Integrations
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Fast motion sensor - I've used this sensor with a Xiaomi Hub for ~9 months, and it responds incredibly quickly (faster than some more expensive sensors I've purchased). I'm still using the original battery.
CAUTION!! The specific sensor has a timeout of 2 minutes. It tracks motion very fast but then stays inactive for two minutes. It is not suitable for several applications.