Latexian: A LaTeX Editor for Mac OS X
tacosw.com/latexian
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Latexian is a revolutionary, new LaTeX editor for the Mac. Latexian provides advanced tools for creating and typesetting LaTeX documents. Using Latexian's Live Preview, you can see how your document typesets while you are editing it the PDF preview updates automatically! Latexian has many other advanced features, including syntax-aware spell checking, tabbed documents, code completion, and much more. Latexian supports the LaTeX and XeTeX typesetters, and includes support for working with BibTeX documents.