SpeedFan - Hardware monitor for Windows that can access digital temperature sensors located on several 2-wire SMBus Serial Bus. Can access voltages and fan speeds and control fan speeds. Includes technical articles and docs.
iStat Menus - "An advanced Mac system monitor for your menubar."
iMac HDD Fan Control - iMac HDD Fan Control is an HDD fan control for the Mac operating systems by using which the Mac users can control the speed and noise of the fan of the Mac.
Stats - Simple macOS system monitor in your menu bar.
smcFanControl - [Download] smcFanControl 2.
MenuBar Stats - Advanced Mac system monitor right from the menu bar