As a webmaster I have faced issues with website being down and non-functional at unseen times, due to a server or network error. That is why I am looking for good monitoring tool that will notify my in an instant manner. What can you say about CloudStats.me regarding my search terms?
For long years I used the free services of ServiceUptime, and proved to serve me good, but if you want real-time instant notifications there are paid plans that let you modify the basic monitoring service as you wish. Check them out, http://www.serviceuptime.com/pricing.php,
I have done some research on their name and can say you can trust CloudStats.me. They have secure and quality service, instant alerting, feature adjustment and low prices.
We offer our server monitoring service with instant email/SMS notifications. Email alerts are free, SMS alerts are very cheap. Monitoring itself is free if you do not want 1 minute monitoring frequency. 1 minute monitoring is provided for a small fee. We support many protocols, have multiple locations, each failure is confirmed from machines on two different continents to prevent false alerts.
I would say that newrelic.com is your best bet. It is free but some really good tools that will do what you need.