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.
I found out something interesting when I’ve gone through my WordPress setting, it seems that the once famous XML-RPC ping sites are either out-of-service or have been taken down.
The one standing up until today is Ping-o-Matic and venerable Weblogs (the first blog XML-RPC ping service).
I once tried to run one of such services to in order to study spam blogs behavior, but it ends up eating too much server resources with too much noise coming from all the submission, I ended the experiment just over one-year.
Probably this is what happening around the world, ping sites gotten shut-down because of being overwhelmed. The remaining option of promoting blog posts is through social status updating site such as Facebook, Twitter and Buzz (also identi.ca!).