New rules in El Capitan have broken a very useful utility – MenuMeters. This preference pane shows very useful information about the performance of your Mac – processor, RAM, network and disk – in the Menu Bar. I’ve used it for about 10 years and find it invaluable.
But Yuji Tachikawa made a very smart connection – that the blocked NSMenuExtras API is very similar to the unaffected NSStatusItem API. The author of MenuMeters, Alex Harper, had made the code available, thus allowing Yuji to make the necessary modifications and provide a working version! I came to it via this discussion on StackExchange.