Also Pyre [0] by Facebook and Pytype [1] by Google. More importantly, the core part (type annotations) allowing these libraries to exist has been added to core python for years now and keeps on evolving, so it is an ongoing effort.
EDIT: As mentioned below, also added Pyright [2] by Microsoft
Having tried a good number of these various type checkers, it seems like Pyright is the only one that properly supports all of the accepted PEP changes to typing.
That already exists, and van Rossum worked on it: http://mypy-lang.org/