Karl Yngve Lervåg sent in vimtex (GitHub: lervag/vimtex), a script with lots of commands and mappings for LaTeX authors. It's inspired by LaTeX-Box, but is written from scratch with extensibility in mind.
Vimtex includes motions for section navigation and moving between matching delimiters, LaTeX-specific text objects,
texcount integration, support for PDF viewers, and it even has completion for citations and labels. There are additional features like mappings and improved syntax highlighting: read more in
The documentation includes details on the project's structure, so you can find out how vimtex initialises and manages state, and defines autocommands. If you're interested in extending vimtex with your own TeX-related features then the documentation helpfully provides enough details to get going!