I assume you have turned on show-paren-mode so matching parens are highlighted:
(show-paren-mode t)
Then this will show the matching line if the paren is off the screen:
(defadvice show-paren-function (after my-echo-paren-matching-line activate)
"If a matching paren is off-screen, echo the matching line."
(when (char-equal (char-syntax (char-before (point))) ?\))
(let ((matching-text (blink-matching-open)))
(when matching-text
(message matching-text)))))