Its always a good option to have monitoring, and there are a lot of options available. If you are interested in uptime and notifications, you can use a service like http://pingability.com

If you are interested in making sure services are up and running, and have more time to spare there are a lot of amazing options out there . A few would include Nagios, Zabbix, Munin, Monit, Cacti, etc

Some of these come in a nice distro package, with a helpful installer, others can be time consuming and difficult to install. Over all, there is no one single answer for any one person, you need to work out what you want it to do, before you choose the package.

Some packages have a web based management system, others just a web interface with the output. Some only monitor downtime, others give you a full statistical breakdown on everything. It all depends on what you need for your problems.

One customer we had, found he had a simple problem which was that the dovecot server died whenever the time was changed at all. eg On reboot the time was checked, updated a few seconds, and dovecot would promptly die 5 mins after booting.

In this case the solution was a small shell script to just check to see if it was responding, and if not, restart it.
Since it was such a neat few lines of code, i decided to take it one step further and wrote a simple monitoring system which works for localhost or remote host, and just calls a command(s) you specify when that port is unreachable, this means it can call a rimuhosting API to reboot, or ssh login to restart things. Feel free to grab a copy of that with examples

cd /etc 
wget http://blog.rimuhosting.com/files/monitor.zip 
unzip monitor.zip
cd monitor/ 
less README

If you need any sort of monitoring or other setup, just drop us an email or submit a ticket. We are only too happy to help give advise and set things up for you.