Low-Cost/Free Service Monitoring

[Ryan Simpkins]

I have a collection of Linux servers providing various services (web, e-mail,
ftp) that I'd like to monitor. I am already using Nagios, but I've seen some
issues latley where a third party service monitoring solution (with decent
geo-diversity) would be very helpful. Because these are personal/secondary
servers I don't want to pay much (free is the best).

So far in my searches the 'best' I've found are these guys:

http://www.alertbot.com

They are $67.92/year for 10 ports (can be on different hosts) using a 5 minute
monitoring interval. A 30 minute interval is $17.40/year. Has anyone used
them? Who do you use?

-Ryan