Suprvise is a real-time health monitoring and errors tracking dashboard.
WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Smaller - Make your websites load faster
Oh Dear! - Website monitoring, without the hassle
Website Grader - Grade your website's strengths and weaknesses in seconds.
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.