You may be interested in http://daringfireball.net/thetalkshow/2016/06/17/ep-158 where Craig Federighi discusses how Apple implemented wear-your-Apple-watch-to-unlock functionality for their Macs; as it turns out, they
make calculations based on how fast the Bluetooth responses are to judge the distance between the laptop and the watch — that way, a snoop can't unlock your laptop if you're merely in the room. It's nice to know that Federighi, at least, is involved in the nitty-gritty even though these aren't reflected in the keynotes.