Track any activities in Mac OS X. Check the spikes and drops in CPU usage, analyze the currently occupied volume of memory, view the battery status of a portable device. Access network activity trackers, manage the disk space, get readings of fan speed and temperature.
XRG (X Resource Graph) is an open-source system monitor for OS X. XRG allows you to monitor CPU activity, GPU activity, memory usage, battery status, machine temperature, network activity, disk I/O, current weather, and stock market data. The goal of XRG is to be a functional system monitor that has a clean and flexible interface, so it doesn't intrude on the rest of your Mac experience.