Stater!

iStat is a series of system monitor apps. It's available in different versions: iStat Menus, iStat for iOS and iStat Server as a companion application to the iStat for iOS app that lets you remotely monitor your computers (free for Windows and Mac).

This is a port to OS X El Capitan 10.11 of MenuMeters by Alex Harper.

MiniUsage displays various data like CPU usage, amount of network flow, battery status and process names which uses much CPU time in a menubar. It takes little space and can display various data, so it's suitable for notebook.

Monitor numerous OS X statistics including: CPU activity System load over time Network bandwidth and activity Memory activity and usage Battery & wireless signal strength Disk usage Current time and date Compact, clever & fully customizable user interface Presents information both graphically and with text Beautiful on Retina display Fits in perfectly with the new system appearances Save & load custom appearances Minimizes impact on system performance View data on the desktop, in the menu bar or Dock Show & hide windows using system hotkeys »

Easily Monitor Your Mac's System Stats.

SysMetrix is a skinnable clock and metering application. Its purpose is to provide system metrics in a variety of interesting, useful, and cool ways. It can monitor and report on the hundreds of statistics

Professional System Monitoring Utility designed for Mac.

Translucent provides detailed real-time information about what is going on inside your Mac. At any given time Translucent displays how much each one of your processors is being utilized, detailed information about how your memory is being used, how much data is being sent and received on your network interfaces and how much is being read and written to your hard disks. It displays itself as small addition to your status bar with tooltip-style detail popups; displaying more detailed information on any of the sensors in the status bar. Translucent also displays its sensor information in windows for larger and more detailed information viewing. »