To install this package, run in Emacs:
M-x package-install RET wcheck-mode RET
A general interface for text checkers Wcheck mode is a general-purpose text-checker interface for Emacs text editor. Wcheck mode a minor mode which provides an on-the-fly text checker. It checks the visible text area, as you type, and possibly highlights some parts of it. What is checked and how are all configurable. Wcheck mode can use external programs or Emacs Lisp functions for checking text. For example, Wcheck mode can be used with spell-checker programs such as Ispell, Enchant and Hunspell, but actually any tool that can receive text from standard input stream and send text to standard output can be used. Wcheck mode sends parts of buffer's content to an external program or an Emacs Lisp function and, relying on their output, decides if some parts of text should be marked in the buffer.