Asciidoctor: http://asciidoctor.org/docs/asciidoc-writers-guide/ . There are forthcoming plans to include a LaTeX backend (https://github.com/asciidoctor/asciidoctor/issues/681 ), but it can already output to HTML and Docbook, which can in turn output to other formats including PDF. There's also MathJax-based equation support for the HTML5 backend: https://github.com/asciidoctor/asciidoctor/issues/492 .

Obviously the big step is for it to be able to output LaTeX so that the equation capabilities and such will be directly exposed, but Asciidoc is pretty awesome already in my experience.