What are some alternatives?
When comparing Ruler and SpeedFan, you can also consider the following products
MailHog - MailHog is an email testing tool inspired by MailCatcher, but easier to install.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Printix - Printix is a cloud-based print management platform.
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.
LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
iStat Menus - "An advanced Mac system monitor for your menubar."