HostMonitor

HostMonitor is a highly scalable network monitoring software suitable for small and enterprise-level networks.
HostMonitor can check any TCP service, ping a host, check a route, monitor Web, FTP, Mail, DNS servers.

It can check the available disk space, monitor size of a file or folder, check integrity of your files and web site; it tests your SQL servers, monitors network traffic and much, much more.
HostMonitor is a network administration software, it provides different ways to respond on failed services. Audio and visual notifications alert people near the machine. E-mail and pager notifications inform a wider range of remote operators. HostMonitor can take actions that are designed to recover from a failure automatically without human intervention (e.g. "restart service", "reboot computer" or "dial-up to the network" actions).