Have you ever wanted to force a script to act differently when it is invoked by cron? If the script is run interactively, for example, you might want the script to prompt the user for some information ...

Not a crontab solution but have a look at iCal alarms. I know they can be set to run when iCal isn't itself open but I don't know if they run when that user is not logged in.

Cron processes, or "cron jobs," may be used to start and stop applications within a Linux or Unix operating system. You can create cron jobs to perform functions such ...