Show org-babel code block being evaluated

(defun org-babel-block-range ()
  "Return the begin and end points of the current src block"
  ;; based on org-babel-mark-block
  (let ((head (org-babel-where-is-src-block-head)))
    (when head
      (save-excursion
        (goto-char head)
        (looking-at org-babel-src-block-regexp))
      (cons (match-beginning 0) (match-end 0)))))

(defvar org-babel-evaluation-overlay nil)
(defvar org-babel-evaluation-timer nil)
(defun org-babel-remove-overlay ()
  (when org-babel-evaluation-timer
    (cancel-timer org-babel-evaluation-timer)
    (setq org-babel-evaluation-timer nil))
  (when org-babel-evaluation-overlay
    (delete-overlay org-babel-evaluation-overlay)
    (setq org-babel-evaluation-overlay nil)))

(defadvice org-babel-execute-src-block (around progress nil activate)
  (unless org-babel-current-src-block-location ;; don't handle this yet
    (let ((range (org-babel-block-range)))
      (org-babel-remove-overlay)
      (setq org-babel-evaluation-overlay
            (make-overlay (car range) (cdr range) (current-buffer) nil nil))
      (overlay-put org-babel-evaluation-overlay 'priority 2)
      (overlay-put org-babel-evaluation-overlay 'face
                   '(:background "yellow"))
      (redisplay)
      (unwind-protect ad-do-it
        (setq org-babel-evaluation-timer (timer-create))
        (timer-set-function org-babel-evaluation-timer
                            'org-babel-remove-overlay)
        (timer-set-time org-babel-evaluation-timer
                        (time-add (current-time) (seconds-to-time 0.1)))
        (timer-activate org-babel-evaluation-timer)))))