Can I use this *only* for motion sensors? about homebridge-hue HOT 1 CLOSED

You can only enable sensors in config.json and disable lights, groups, etc., see the README. Note that this will expose all sensors to homekit, not just the motion sensors.

I think the hue motion sensors are great value for money, but the standard hue app doesn't do them justice. I actually control my lights through manually created hue bridge rules (so they work even when homekit doesn't feel like it), any I control my Sosos speakers through homekit rules (and another homebridge plug-in, which I haven't published yet). When I enter a room, the lights (when it's dark) and speakers turn on automatically. Leaving a room off is a bit more complicated, as the sensor detects motion, not presence. I'm actually using a CLIPGenericStatus sensor to keep a presence state and the motion sensors in the adjacent rooms / hallway to detect leaving a room. The lights and speakers only turn off automatically (after 5 minutes) when motion detected turns off within 15 seconds of motion detected turning on in an adjacent room.

from homebridge-hue.