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.
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.
IP Messenger A simple LAN messaging client based on TCP and UDP over IP supporting AES and RSA encryption.