Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
socat - socat is a relay for bidirectional data transfer between two independent data channels.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Simple Port Forwarding - Simple Port Forwarding works with WebPages and not directly with your router.
Better Uptime - We call you when your website goes down
AUTAPF - Reliable TCP and UDP port forwarding for Windows.