Has anybody come across these before? https://getkubu.com/
Just had 2 new composite doors installed and there was labels in the door jamb about these, I scanned the QR code and was able to enquire about the sensors. They are actually free and included with my doors (in the post to me now!)
From what I can see, they actually sense whether the door lock is locked or not and then you can install a App which can notify you if you leave the geofence area and doors or windows are unlocked :o
I have emailed them for more technical information, it would be great to be able to integrate these with HA. They seem to have been out for a few years here in the UK, but its the first I had heard of them.
https://getkubu.com/manual/