I am looking for a text-editor with full unicode-math support. Plaintext math entered and rendered properly. I am not expecting typographical features and symbol-repositioning like LaTeX, but at least render the symbols linearly. And of course input method for it, so I do not need to copy and paste.

Is there such an app available? (anywhere, not just repositories)

Note: I do know about OpenOffice, LibreOffice, Word, TeX, LaTeX, MathML, etc; but I want plaintext!

This webapp is the closest that I could find.