SQL for status duration Stack Overflow question

gistfile1.txt

CREATE TABLE `data` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `set_point` float DEFAULT NULL,
  `temp` float DEFAULT NULL,
  `on` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`id`)
);

INSERT INTO `data` (`id`, `timestamp`, `set_point`, `temp`, `on`)
VALUES
	(341, '2014-12-29 07:59:59', 17.5, 12.7, 1),
	(342, '2014-12-29 08:09:59', 17.5, 12.8, 1),
	(343, '2014-12-29 08:20:00', 17.5, 12.8, 1),
	(344, '2014-12-29 08:29:58', 17.5, 12.8, 0),
	(345, '2014-12-29 08:39:59', 17.5, 12.9, 1),
	(346, '2014-12-29 08:49:59', 17.5, 12.9, 1),
	(347, '2014-12-29 08:59:58', 17.5, 12.9, 0),
	(348, '2014-12-29 09:09:59', 17.5, 13, 0),
	(349, '2014-12-29 09:19:58', 17.5, 13, 0),
	(350, '2014-12-29 09:29:59', 17.5, 13.1, 0),
	(351, '2014-12-29 09:39:58', 16, 13.7, 1),
	(352, '2014-12-29 09:49:59', 16, 14.1, 0);