Trying to create a cron job to run if a condition is true

Adding a cronjob that execute a specific function in CI is very simple. Here is an example of one running at 1am every day.

Code:

00 01 * * * php /path/to/codeigniter/index.php controller my_function >> /dev/null

The function your cron is executing should do all the work of checking if a reminder should be sent out or not.