Review: Level Bolt is a stealthy smart lock contending with an imperfect world – Six Colors:

The Bolt is unlike most other smart locks in that it doesn’t replace your existing deadbolt. Instead, it fits inside your door, basically sandwiched in between the exterior keyway and the interior thumb turn. Inside sits a small motor with a Bluetooth chip, which can turn to shoot the bolt itself.

The engineering and design of this device is extremely clever. From the outside, the Bolt is completely invisible. The only place you can even see the device is the bolt itself, where Level’s logo is embossed on the end. (In another particularly ingenious piece of engineering, the bolt also contains a replaceable CR2 battery that powers the whole assembly. Swapping it out just requires unscrewing the end cap.) Another plus: the existing key and thumb turn for the deadbolt work exactly as before, and don’t interfere with the smart lock, or vice versa.

Great review of the one smart-lock I’ve tried myself… The design is fantastic, and if anything simpler than the original hinge mechanism that came with my deadbolt, and fairly reliable for my bluetooth usage.