I never wanted to control the door lock via my smart-home system. 
It always seemed too risky. 

So I added the capability to only monitor the state of the front door (open/closed) and the lock of the door (locked/unlocked). 

The door state is monitored with a magnet and reed switch combination, the lock via an inductive proximity switch on the frame.

The states are captured with my Arduino remote I/O 

(https://hackaday.io/project/167904-diy-scada-wireless-remote-io)
and sent to the software PLC. 

The inductive proximity switch can sense the latch through the wood of the door frame.  

A 3d-printed part and hot glue hold it in place.(no drilling required)