libsysactivity is a lightweight library that retrieves statistics of the system's activity in a portable and thread safe way. In each OS that it supports, it offers the same API for retrieving the activity of Hard disks, CPUs memory, Processes, Network interfaces, Memory, and Swaps.
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.