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.
Artica Proxy - Artica Proxy is an appliance that claim to manage Squid-cache proxy with all features that Squid...
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Polipo - A small and fast caching web proxy (a web cache, an HTTP proxy, a proxy server).
Better Uptime - We call you when your website goes down
Privoxy - Privoxy helps users to protect their privacy.