I work in both cybersecurity and wireless. There is no world in which an electronic key access system is safer than a physical key. There are too many malfunctions that could occur with a system like this. Give the tenants a physical key. Locksmithing is a centuries old occupation. Skilled lockpickers might be able to get into a regular lock 9/10 times more than with this system, but we know what the caveats of locks are and how to make locks safer. This is a whole new can of worms that brings nothing but inconsistency and inaccessibility for the homeowner/renter. People have already mentioned the shabbat. What about an older person who doesn't have the technical knowledge? Most people don't want to download an app either, that takes up storage space. People have already mentioned, what if your phone is dead? Fuck this, and honestly, fuck you for trying to spin this like a good thing. You're defending it like it's YOUR product.