https://www.theverge.com/circuitbreaker/2017/8/22/16179374/latch-apple-homekit-smart-lock-announced

Latch is introducing a new smart door lock today that can be controlled with an iPhone. It’s called the Latch C, and in addition to iPhone control through Apple’s HomeKit platform, it has all the same smart features as the original Latch door lock: a built-in camera to see who’s at your door, the ability to use passcodes and cards instead of a key, and a recorded log of who’s come through.

The Latch C is much smaller than the original Latch lock, called the Latch M, because it’s designed for a different type of doorlock. Where the Latch M was built for tall mortise locks, the Latch C is meant for simpler cylindrical deadbolts, which aren’t attached to the knob. That allows the unit be a lot smaller while still offering the same features — though it also means that, like the M, it can only fit on certain types of doors.