I'm looking for an application that can run remotely to periodically check a webserver to ensure that it's delivering pages. I can't use one of the free web-based services because the servers I'm monitoring are closed to the outside internet. I have internal client machines I'd like to install the monitoring tool onto that can check specific URLs in both HTTP and HTTPS. Then email a notification when something stops responding.

It would be nice to have a tool that is platform agnostic (written in perl, python, etc.) so I could have flexibility in what type of client machine I use for the monitoring.

Any recommendations appreciated. Everything listed at freshmeat.net is many years old without a recent update.

I'm afraid I can't recommend anything that is platform agnostic, but Nagios will monitor almost anything.

When properly configured, it is fast, reliable and extremely flexible. I have used it to monitor over 1100 services
across 100+ machines.

Do you wish to monitor Internet websites as you mentioned that web server application should check HTTP and HTTPS URL`s? If yes, Websense Internet access management system is the best one suited as per your requirement. In case you also wish to monitor computers remotely, I would suggest installing on premise remote support appliance such as RHUB appliances.

Httperf is a tool for measuring web server performance. It provides a flexible facility for generating various HTTP workloads and for measuring server performance. It is product of hp.