Keeping an eye on your Mac's hardware and resource usage is helpful, but there is no accessible way to do so without third-party utilities.

Stats is an open-source app designed to help you monitor temperature, voltage, power draw, battery level, as well as general resource usage, from the menu bar. It is fully configurable, unobtrusive, and quite easy to use.

iStatistica Pro lets you overview your battery statistics, realtime informations about CPU, RAM usage and much more. Network statistics includes external, gateway and local IPs, speed and data rates chart.

iStat Menus lets you monitor your system right from the menubar. Included are 8 menu extras that let you monitor every aspect of your system. iStat Menus 6 sports a completely new design — new menubar icons, new dropdown menus, and the app and icon itself have all been redesigned to be cleaner, clearer and more at home on Yosemite. Menubar graphs can now use dark backgrounds, improving legibility.

iStat Menus lets you monitor your system right from the menubar. Included are 8 menu extras that let you monitor every aspect of your system.