Uptime monitoring service

I need a cheap and reliable way to monitor my sites.

[seanski]

I am a reseller and having some issues with downtime from the company I'm using. Anyone have a suggestion for good monitoring service that will alert me when a site is down (currently about 40 sites) and provide monthly reports that I can share with the company I am using and/or give me enough data to know if I need to change to a different company?

[coopster]

Welcome to WebmasterWorld, seanski.

Can't get much cheaper than an open source project -- Nagios [nagios.org]

[seanski]

Thanks Coopster. I failed to mention my sites are on windows. It doesn't appear Nagios works on windows. I will read further in their site to be sure.

[henry0]

From Nagios' doc:

System Requirements

The only requirement of running Nagios is a machine running Linux (or UNIX variant) and a C compiler. You will probably also want to have TCP/IP configured, as most service checks will be performed over the network.

You are not required to use the CGIs included with Nagios. However, if you do decide to use them, you will need to have the following software installed...

A web server (preferrably Apache)
Thomas Boutell's gd library version 1.6.3 or higher (required by the statusmap and trends CGIs)

[Mr Bo Jangles]

I have used websitepulse for a few years. I pay a low amount per month - and I have two servers monitored, I get e-mail and cell phone alerts - seems pretty cheap to me - I believe there is even a level of service they have that is free.