In the great variety of monitoring tools I found one, which seems to be a great one along with being a free tool. It's Mon.itor.Us- a free website monitoring solution. It offers elegant, easy-to-use, web-based solutions for individuals, enterprises and solution providers. Since it is a hosted service, you don't need to maintain an in-house server, install and configure complex software, or spend time to maintenance. All you need is a web browser and an internet connection. The approach is called on-demand or software as a service (SaaS), which provides significant cost and simplicity benefits over the traditional software model.