iPulse 4+

I've used iPulse from icon factory since it was introduced. It can be re-size for any monitor. I have it the corner of my second monitor. What makes this shine is at a glance to can see "Real time" what your computer is doing, CPU usage, drive activity, network access and more, in an attractive little circle. I would recommend going into preferences and turning on "Show Text"for CPU usage, memory in use, total disk space used on startup disk, and Network activity.
Pros: At a glance to can see your CPU usage (aka. why is my computer acting slow), or your disk storage is now full. Also with a right click on the center you can get to diagnostic tools like Activity monitor or network utiltiy.
Cons: This really doesn't show an extreme indepth view of your computer activity. It also doesn't have graphs of activity over time. If you want that, get iStatisitica Pro. Also iPulse comes with 7 customizable Graphical looks. When iPulse was first introduces devs made dozens of custom Graphical looks for iPulse. I'm using Purple Turbine. Wish icon factory would sell the others as a package, as a in App purchase.

I've been a big fan of iPulse for many years.

Something changed with macOS catalina, however - since the upgrade, iPulse can't tell me how full my hard drive is. Used to work fine. I hope an update is coming.

I was hoping for more information, e.g. temperatures (yes, if I were to pay more attention to the description...). That is the problem with things you cannot preview. It is only after downloading and running that I realized what the circle icon did and that is pretty much all it does. You can click on the icon and see details, but selecting where to click is problematic to see what you want to see. You have to get used to the colors or to the “o’clock’ position to click. I suppose once one gets used to using it 24/7 for a few weeks, it becomes more user friendly but I am not that patient, sorry.