Monitoring an URL / Heartbeat, if not available turn off WAN2-Interface

[zaphod_beeblebrox]

Hi,
We have a setup in which we need to switch over to another server if an internal (LAN) URL is not responding in the right way.
The switch over will be done by an external router if it detects a link failure. So, my approach would be:

• Monitor the internal URL via curl/grep in a 1/min cron job
• If the cronjob detects an error it should switch down WAN2
• Switchback should be done manually

How would I accomplish this in pfSense the best way? Or in other words: is there a better way than putting this script on the firewall (maybe there are some monitoring packages which I don't know).

Thanks for your advice,
Matthias