menumeters

Install command: 
brew install --cask menumeters

Name: MenuMeters for El Capitan (and later)

Set of CPU, memory, disk, and network monitoring tools

https://member.ipmu.jp/yuji.tachikawa/MenuMetersElCapitan/

Cask JSON API: /api/cask/menumeters.json

Cask code: menumeters.rb on GitHub

Current version: 2.1.6.1

Requirements: macOS >= 10.15

Analytics:

Installs (30 days)
menumeters 172
Installs (90 days)
menumeters 480
Installs (365 days)
menumeters 1,991