I just shared i18n-tasks. Rails I18n tasks to find missing / unused translations and more. Works with slim / coffee / haml etc. Provides these tasks:

• i18n:missing task shows all the keys that have not been translated yet
• i18n:unused task shows potentially unused translations
• i18n:prefill task normalizes locale files, and adds missing keys from base locale to others </ul> i18n:unused will detect pattern translations and not report them, e.g.:

  t 'category.' + cat.key # 'category.books' considered used
  t "category.#{cat.key}" # also works