The Aqara U400 is one of the more interesting recent smart-lock designs because it uses ultra-wideband positioning rather than only Bluetooth proximity. The goal is a door that unlocks when an authorized person actually approaches, without fumbling for a phone or tapping a watch.
The product also advertises Apple Home Key and Matter-over-Thread integration. The important shopping questions are hardware compatibility, door dimensions, the exact phone/watch support list, battery life and how the lock behaves when network services fail. A smart lock is only useful if it is boringly reliable.
Do this: compare the U400’s requirements with your door and Apple devices before treating hands-free entry as a real upgrade.