Aqara UWB Smart Lock U400 Review: Is the Prime Day Price Worth It?

The Aqara U400 uses Ultra-Wideband for hands-free unlocking that's more precise than typical Bluetooth locks — here's who it actually makes sense for at this Prime Day price.

What UWB actually changes about a smart lock

Most smart locks use Bluetooth for auto-unlock, which means your phone triggers the lock while you're still halfway down the block — or worse, from inside your car. The U400 uses Ultra-Wideband, the same short-range positioning tech in Apple AirTags, to detect your precise distance and approach angle. The result is auto-unlock that fires when you're actually at the door, not twenty feet away. Aqara has solid Apple Home and Matter integration, so it fits naturally into an existing smart home setup without forcing you into a proprietary app ecosystem.

The catch: UWB only works if your phone supports it

Here's the limitation worth knowing before you buy: UWB hands-free unlock requires an iPhone 11 or later (or a compatible UWB Android device). If your household has older phones, you'll fall back to standard Bluetooth auto-unlock or keypad entry — which works fine, but you're paying a premium for a feature you won't fully use. At $219.99 from a typical street price around $270-280, this is a meaningful discount. If you're already in the Apple ecosystem with a current-gen phone, it's a genuinely good time to pick this up.