FreeBSD sends emails to 'root' user by default. If you take time to read them, you get a pretty decent overview of the system. Other than that, you need to be

FreeBSD sends emails to 'root' user by default. If you take time to read them, you get a pretty decent overview of the system. Other than that, you need to be more specific. There's not one solution to monitor everything. Nagios runs on FreeBSD, snmpd is another widely used alternative, etc.