The sysmon plasmoid is based on KDE standard system load plasmoids which are constrained to some chosen metrics like CPU load. In contrast, the sysmon can show any metric provided by the System Monitor data source engine.
Installation is pretty simple and straight forward:
$ git clone https://github.com/burlog/plasmoid-sysmon.git plasmoid-sysmon
$ cd plasmoid-sysmon
$ plasmapkg2 -t plasmoid -i ./plasmoid