Is there a tag for pir/motion sensor ?
Why would you want to send a command to a motion sensor?
You wouldn’t, but you don’t send a command to a temperature sensor either, and that have a homekit tag for getting information from OH into Home. So it would be to use a PIR/motion sensor as an actor in Home automations.
I think Homebridge supports more device types. But I like the convenience of the built in addin.
Those tags are for reading the sensors value which is more or less a static value (at least for a certain amount of time). But a motion sensor would give you only a short pulse (although one can extend that pulse duration with config parameters for a lot of devices).
So I guess the answer is no but I’m not sure 
I just wanna see if my door is open or if we have motion in the bedroom 
yeah a contact sensor would be useful, and fairly static like a temp senor (to take @sihui’s point).