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.
Traq - Traq is a PHP powered project manager and issue tracker featuring multiple projects, milestones...
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Bugify - Bugify is a simple PHP issue tracker, designed to offer powerful bug tracking capabilities in an easy to use system.
Better Uptime - We call you when your website goes down
jtrac - JTrac is an open source and highly customizable issue-tracking web-application written in Java.