Is this a different method from the httptap [1] that was on hackernews a few weeks ago? Somebody in that post seemed to say that it also generates CA certificates on the fly.
httptap is really cool! Their technique is different (they do a filesystem mount instead of intercepting syscalls like Subtrace does) but both tools effectively reach the same goal using different routes.
[1] https://news.ycombinator.com/item?id=42919909