I have 3 philips motion sensors working through ST, through a custom device handler.
My kitchen one stopped picking up any motion or anything so ive since removed it, im trying to re add it. If i remember correct, i add a thing, then go into the device handler and select hue motion sensor and that should be it? Tried that and it is within ST now but ive clearly not set it up correct, its just constantly saying “motion” and the config area has nothing inside it, wheras my other 2 sensors do. Please help 
I would like to do this as well, where did you get the device handler from please ?
I cant actually remember now which one i used. I think this is why im struggling to re integrate this again
Try resetting the motion sensor before trying to re-add it. You will need to hold down the reset for at least 30 seconds for it to reset properly.