In its most simple form, EventSentry (Light) can ping an IP address and alert you if the remote host become unresponsive. Simply adding a host to EventSentry should provide this type of monitoring. Under Packages -> Event Logs -> Heartbeat Alerts you can find the filter rules that would send you an email alert when a host changes its ping status. The notification is sent to the Heartbeat Alert action by default (Actions -> Heartbeat Alerts).
There are additional ways to monitor a server more thoroughly, depending on the remote OS and the level of access you have. I'd be happy to provide more info if you could let us know.
I hope this helps.