Has anyone heard of “Pingdom”?
It supposedly monitors your website and lets you know if it went down…
What do you do to monitor your site?
Debbie
Yep, I used a free account a while back. It worked perfectly fine.
Any Open-Source solutions out there?
How important is it to be using something like Pingdom for a live site?
Debbie
I can’t say that I’ve looked into it. The reason for this is because it doesn’t make any sense to have a pinging service on the same connection as the one that you are trying to monitor. If the connection goes down, then you’d never know because the pinging service wouldn’t be able to notify you.
The whole idea of a monitoring service is to have it situated externally so you can have it notify you as to when the outside world sees a problem with your site/server/connection.
How important is it to be using something like Pingdom for a live site?
It depends on how much you are concerned about uptime and downtime.
For my personal sites, I don’t monitor them, as they don’t get much traffic. For business sites, sure, I monitor them.
If you’re looking for something to run yourself, the best-known OS software for this kind of stuff is Nagios.
But, as Force said, you’ll want to run this on a separate machine, preferably in a different data centre than where your site is hosted. It’s also meant to monitor entire infrastructures, not just single websites 
To be honest, even though it’s OS software, you’re going to need to spend some cash to set this up. If you’re running a small site it’s much better to use a free PingDom account (I do, for my personal site). For professional, high load/ hightraffic sites, your hosting partner should already have something like Nagios set up.
Just started to use Pingdom at work, as a bit of a trial for remote monitoring with SMS notification - this is smoething where Open Source solutions tend to fall a bit short - not having notifications beyond email which makes relying on them a little harder.
Hopefully it’ll work well 
Pingdom works great and I have used it since it has been open for business. Also, you may check out Montastic… it is a free monitoring service that has been reliable for me.