(defvar navi2ch-message-before-send-wait 120)

(defun navi2ch-message-before-send-insert-wait ()
(when current-prefix-arg
(let ((sec (if (numberp current-prefix-arg)
current-prefix-arg
navi2ch-message-before-send-wait)))
(message "Sleeping for %d seconds..." sec)
(sleep-for sec)
(message "Sleeping for %d seconds...done" sec))))

(add-hook 'navi2ch-message-before-send-hook
'navi2ch-message-before-send-insert-wait)