Seems a bit dead in here but I'll give this a shot.
I'm looking for a small in-ceiling (not ceiling mounted) movement sensor. I don't want one that operates off high voltage e.g. ones that operate lights. Ideally it would be an alarm type sensor but as long as it operates off 12V and can trigger an output (dry contact) then I'm happy.
I've been looking quite hard for some and almost any that come are either massive, ugly or cost an absolute bomb. Does anyone have any ideas? It doesn't have to be super fancy, I just want it to be able to detect basic movement.