PortSensor is a powerful Windows/Unix server monitoring tool with Linux/Mac/Windows clients. Sensors can be created to monitor nearly any TCP/UDP service, such as: HTTP, FTP, POP3, SMTP, MySQL, and DNS. Custom sensors can be created to monitor your other critical server metrics, such as processor loads, mail queue loads, disk space usage, and log activity.
x11vnc allows one to remotely view and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. It is designed to be compatible with all Unix variants and Mac OS X, and depends on a small set of standard libraries. It supports SSL/TLS and VeNCrypt encryption, Unix password logins, single port access, Zeroconf, file transfer, and UltraVNC extensions. It is part of the LibVNCServer project.