I'd like to be able to view my cpu and memory usage in real time. Not as a desktop widget or window application, but as a widget in the menu bar. Is this possible?
iStat Menus has the functionality you are asking for. It is available starting at USD$18 for a single license.
I use MenuMeters for this functionality, and have a hard time living without it. How do other people know when their web browser is finally done downloading a page, or YouTube stalled out, or iPhoto still working, or ...?
MenuMeters is freeware, but well worth the donation.
The original author has stopped maintaining MenuMeters, but someone new has taken over for El Capitan.
I made a simple app that displays cpu and memory usage on menubar, free and open sourced. Feedback is welcome.
Check out iGlance it's open source.
I prefer SystemPal. iStat itself consumes too much CPU and RAM. SystemPal is quick, tiny, configurable, neat, and powerful. It's available on Mac App Store.
I created a free app that shows percentage on the menu bar:
You can download it from here:
A free open source solution is CpuInfo on GitHub (shows cpu only)
Or you can try some geeklets from the internet (or make one yourself) on Geektool. I find it more customizable than menu bar apps, and prettier when I get to use the fonts and sizes I like.