The ZY-M100 is the sensor that made whole-home presence detection a realistic goal. At this price you can put one in every room of a house for the cost of a single FP2. It reports occupancy, illuminance and target distance to Home Assistant as separate entities, which gives your automations more to work with than a simple on/off motion sensor ever could.
The catch is the buying experience. The same product name covers WiFi and Zigbee models, and 5.8GHz and 24GHz radar versions, sometimes within one listing. You want the 24GHz Zigbee variant, full stop. The 5.8GHz version false-triggers on fans and through thin walls, and the WiFi version floods your network and depends on Tuya cloud unless you go through extra effort.
Out of the box the sensitivity is set too high and it will report presence from the hallway outside the room. Drop the sensitivity a couple of steps, set the detection distance to match the room, and it settles down into a genuinely reliable sensor. Zigbee2MQTT supports it natively, so all the tuning happens from the Z2M interface.