The interface of "https://translate.google.com/" by MozRepl.

google-translate-mozrepl.el

(require 'comint)
(require 'url-util)
(require 'moz)
(defun translate-google (&optional flag)
  (interactive "P")
  (let ((lang (if (null flag) "en/ja" "ja/en"))
        (text
         (let ((end (if (use-region-p) (region-end)
                      (forward-word) (point)))
               (start (if (use-region-p) (region-beginning)
                        (backward-word) (point))))
           (buffer-substring start end))))
    (comint-send-string
     (inferior-moz-process)
     (format
      "content.location.href = \"https://translate.google.com/#%s/%s\""
      lang
      (url-hexify-string text)))))

(global-set-key "\C-x\C-t" 'translate-google)