A Trusted Spare-Key Locker for the Block

The idea

I got locked out and realized my only options were a locksmith bill or a key under the mat. I want a small lockbox system for a street or apartment building where a few neighbors register as key-holders, and there's a simple log of who has access to whose spare. It's not about strangers, just formalizing the thing people already do informally so it's safer and someone's actually reachable when you're stuck outside.