KAlarm lets you schedule personal messages to display, audio files to play, commands to execute, or emails to send. Among its options, it allows you to choose the message font and color, recurrence schedule, whether to display an advance reminder, whether to speak the message or play a sound when it is displayed, and whether to cancel the alarm if it can't be triggered on time (e.g. if you are logged out at the time). As well as using the graphical interface to configure alarms, you can use the command line, and there is a D-Bus/DCOP interface for other applications.
Sentinella is a desktop application that monitors your system activity and, when a condition is met, takes the action that you've chosen. While monitoring your CPU, memory, hard drive, and network usage, Sentinella can be programmed to take specific actions when setpoints for utilization or time are met. It can power off, reboot, or hibernate your system, kill an active process, throw an alarm, or execute any command. Sentinella integrates perfectly with the main desktop enviroments (KDE, GNOME, XFCE, and others) and works under many Unix systems.