Python System Monitor (Psymon) is a cross-platform task and performance monitor. It features global process monitoring, system load history (CPU, memory, network, and disks), disk information, network connections, detailed information and CPU, and memory percentage history per process.
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.