MONIT Is a Free System Monitor for Mac That Sits in Your Notification Center
Mac: System monitors are one of those app brands that are nice to have around, but most of us don’t feel like paying for them. If you don’t mind a bit of simplicity, MONIT is a free, open source system monitor found in your Notification Center.
MONIT is a Action Center widget based on the much more complex Monit system monitor . With it, you can get an idea of some of the basic performance data on your Mac, including your processor, memory, disk, network information, and battery usage levels. When you click on one of the options, you will be presented with a drop-down list with more information. It’s not as customizable or complex as we picked the best system monitor, Monity , but as a free solution, it should help most people.
MONIT (free) | Mac App Store via Hacker News