ReLock: Recycling and Upcycling old 2nd hand electronic door locks
A lot of old electronic locks are appearing on the 2nd hand market, many of which no longer work.
I've just started trying to adapt some of these from their old proprietary centralised authentication setup to be easily enabled as local smart locks.
NFC seems to be the ideal solution to re-using and expanding some of this older technology.
Even some modern smart locks are effectively 'bricked' by the manufacturer when they are re-sold.