You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
How much can be gleaned from the official Darwin implementation on these devices? I'm assuming most of the "useful" stuff is proprietary drivers, etc.?
Good question, I actually haven't looked yet! There are also already existing projects that have done some of the work. Obviously the first step is recon and gathering as much existing info as possible. Most of the work though (GPU) is definitely nowhere to be found.
FWIW I've found archives of Apple's Open Source releases like these useful for navigating changes:
https://github.com/apple-open-source/macos …
https://gitlab.com/opensource-saurik/apple …
https://github.com/kallsyms/apple-opensource …
Might be the odd nugget of useful knowledge or at least a lot of hay. 
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.
