I have tested dozens of smart locks over the years for HomeKit Weekly, from the August lock to the latest Level Lock Pro. They all solved the problem of having to fish your keys out, but they never quite solved the problem of “my hands are full.” Even with Home Key, you’d still have to either get your Apple Watch to your lock or pull out your iPhone. Yes, plenty of locks offer various flavors of auto-unlock, but none are perfect and work 100% of the time. That is the problem Ultra-Wideband (UWB) technology aims to solve. This week, I am taking a deep look at the Aqara UWB Smart Lock U400.