There is no lack of application options in OS X to monitor important information on your Mac such as CPU, RAM, storage, network, battery, among other things. To name two, we are already talking about iStats Menus (which is in the menu bar) and Monity (which runs in the Notification Center).
But why then talk about one more? Although they are great apps, the two we mentioned above are paid. The tip, today, the MONIT.
The app also runs on the Notification Center and, although free, is quite complete. It is true that paid users usually present more information about the Mac, but I have no doubt that MONIT's options are sufficient for most users.
Just click on the monitoring circles to expand the information linked to them, such as the CPU usage, how many processes are running, which GPU the Mac is using (if it has two), the memory usage, battery data ( conditions, cycles, temperature, age, health, etc.), the free space available (not only on your Mac but also on the Time Capsule external drive, if you have one and are using it to make backups with Time Machine), in addition to network information such as public IP, upload and download.
Thanks, you have nothing to think about! ?