Re/code:

August Smart Lock, an electronic lock that provides keyless entry into the home, started shipping in limited quantities this week to consumers who placed orders on the company’s website.

The device…lets people unlock their doors using a smartphone app (instead of a key).

The electronic lock replaces the interior portion of an existing deadbolt lock and opens whenever you, a house guest or the cleaner approaches with the right virtual key stored in the smartphone app.

The second to last sentence in the piece might be even more important/interesting and I think it is the future of any Apple wearable.