Quick Ping Monitor A useful and powerful IP monitoring application which supports tens of thousands of single machines on a network.
PRTG Network Monitor Network monitoring utility which displays visual elements like graphs for WiFi and LAN usage in a web browser with an array of advanced usage statistics.
Ping Alert Able to ping one or multiple hosts (HTTP, SMTP) to check whether they're currently online and sends an email if a host is not responding or otherwise unreachable.