What are some alternatives?
When comparing SpeedFan and gauchosoft.com XRG, you can also consider the following products
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
iStat Menus - "An advanced Mac system monitor for your menubar."
iPulse - Using its concise and appealing user interface, iPulse graphically displays the inner workings of macOS on you desktop, menu bar or Dock.
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)
Core Temp - Nov 4, 2017 - Core Temp is a compact, no fuss, small footprint, yet powerful program to monitor processor temperature and other vital information.