It is undeniable that uptime is important for business and personal websites. For example, a website with low uptime may mean that the host is having technical problem or the web server is overwhelmed by client requests (serving web pages may incur a lot of overhead)
Pingness.com service does not require sign-up, you need to submit your email address and website url, and pingness will send reports of your site downtime (if any) and when the website is back-online.