This library for CodeIgniter is made to work with any authentication library.

It only needs a user ID that can be generated per session or pulled from a users table.
You will see that I am getting my user ID from the tank_auth authentication library.

CREATE TABLE `online` (
 `user_id` int(11) NOT NULL,
 `time` int(11) NOT NULL,
 UNIQUE KEY `user_id` (`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin