Really small suggestion, not really worth it's own thread but there's not really any 'collaborative' thread for small suggestions like these. That I know about, atleast.

Anyway, could the door's state_out be changed to 0 when closed, 1 when opened rather than nothing when closed and 1 when opened? Or is a signal of 0 effectively the same as no signal at all. (At the moment there's no way to distinguish between whether a door's state_out is simply disconnected or it's actually closed, which would be handy for people such as me who wish to make alarm systems for doors.)