https://github.com/nschum/auto-dictionary-mode.git
git clone 'git://github.com/nschum/auto-dictionary-mode.git'
An automatic dictionary switcher for Emacs spell checking
Add the following to your .emacs file:
(require 'auto-dictionary)
(add-hook 'flyspell-mode-hook (lambda () (auto-dictionary-mode 1)))
Then just type. When you stop for a few moments `auto-dictionary-mode' will start evaluating the content.
You can also force a check using adict-guess-dictionary, whether or not
auto-dictionary-mode is enabled.
If you're unhappy with the results, call adict-change-dictionary to
change it and stop automatic checks.
You can use adict-change-dictionary-hook to hook into any of these changes,
or adict-conditional-insert to insert text (like signatures) that will
automatically conform to the language.