Hi all 
Just wanted to share my take on the idea, this is such an awesome idea! 
First I took my Xiaomi door sensor and soldered on the contacts.
Then I soldered the ends of the wire on to two battery springs which are glued on to a piece of cardboard. Also had to glue a piece of tinfoil of the deadbolt to make the contacts trigger.
Ran the wires and stuffed the board back into it’s case.
NOTE 
My sensor was being really unresponsive/reporting the wrong state at first. I had to try all sorts of position for my sensor, and finally found a spot where it works.
Now it works! Huge thanks to everyone for sharing the idea 
!
