Munin plugins (Used under FreeBSD 8/9/10/11/12). Most of these plugins are FreeBSD specific. Some plugins are forked from other authors with minor changes (mostly Linux to FreeBSD changes, category simplification, etc.).
As I switched from Munin to Zabbix few months ago these plugins are NOT maintained anymore and I will not test them with upcomming FreeBSD versions. Take it, use it.
Use it if you like it