I’m looking for the same thing for a long time. Either with Shelly1 or sonoff mini.
The S1&S2 of the Sonoff mini are in principle ‘potential free’. So if you directly connect the motion sensor, it needs some sort of power supply to operate. I think you don’t want the motion sensor to put 240V on S1 or S2.
There is a blog post from Itead about new modes of S1&S2 where it looks like showing 3.3V supply!?
There is another post where a schema is shown with 2 motion sensors(PIR) and a sonoff mini. The motion sensor requires external power and only a ‘trigger’ wire is connected to the Sonoff mini. I’m not sure about the voltage for ‘high’/‘low’, but I suppose 3,3V. Not sure. Also the motion sensor will frequently send signals that you have to filter out. I would just use the first ‘detect’ and use Homeassist for the fur logic(time for off, etc.)
I hope on some help/advise on this, because I’m not sure.