Comment by eightysixfour

There are a number of mmWave occupancy sensors that are more than capable of this. The biggest issue is the delay introduced in most smart home contexts by Zigbee and the hubs. Matter/Thread should help here.

Existing options: https://smarthomescene.com/reviews/best-mmwave-human-presenc...

The Aqara FP2 should be out in Q2 with Matter support and be a nice upgrade. It can segment a room into multiple spaces and detect 5 people.