I'm in the process of selecting/purchasing/installing electric strikes. For those unfamiliar with them, it's basically a way to lock and unlock the latch itself that the door's bolt fits into.
In this way, they can work with just about any (non-deadbolt) door lock. You can even continue to use the key to open it, just in case the power's out.
I plan on having an ESP32 that will provide door closed/open status with a reed switch, and also an accelerometer inside the door itself that (experiments pending) might provide door motion telemetry while it opens and closes but also possibly door knocks and attempts to kick it in.
I have plenty of gpio pins left over. And what I'd like to do is to be able to detect the status of the door lock itself. If such a feature exists, I don't even know what to search for. I'm hoping to figure out a way to retrofit it myself. Considering that the lock is entirely mechanical, I thought that perhaps I might manage to stuff something optical into it that would be able to tell if a beam was interrupted. But I don't have a clear idea on how that might be accomplished... the lock itself can probably be disassembled and might have some room to fit very small components into it. Wiring for those will have to be threaded through the door and into the frame on the hinge side though (was planning on doing that for the accelerometers anyway).
It would only need to be able to detect locked/unlocked status so that someone could be warned, it wouldn't need to be capable of locking or unlocking.
Does anyone have any insight?