Diskus is a high-level hard drive diagnostic and limited repair tool. It checks the disk geometry by writing numbered IDs into the sectors of the hard drive. Later one can verify that these sector-IDs on the disk are still correct, thereby detecting data which was not correctly written. There is an option to "freshen" the data on your harddrive, which will read and rewrite the sectors. With modern drives this will re-map defective sectors.
Secrond is a light-weight cron implementation that allows running of user-specified programs at periodic scheduled times, handling tasks in intervals of seconds rather than minutes, as well as hours and days. While it is possible to achieve similar behavior by using a traditional cron daemon and adding calls to sleep() to the programs executed, it is impractical.