MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)
iStat Menus - "An advanced Mac system monitor for your menubar."
Stats - Simple macOS system monitor in your menu bar.
Hardware Lister - lshw (Hardware Lister) is a small tool to provide detailed information on the hardware...
iPulse - Using its concise and appealing user interface, iPulse graphically displays the inner workings of macOS on you desktop, menu bar or Dock.
GKrellM - GKrellM is a single process stack of system monitors which supports applying themes to match its...