Create custom PFsense Script and Package

We are currently looking for someone that can develop a simple and custom script and create a package to install on a PFsense Firewall. This script should monitor our 2 IP addresses (IP 1 and IP 2). Our client (IP PHONE) can only connect to ONE of those IP addresses. This script should therefore monitor the first and the second IP addresses (such as PING every x seconds) and if one goes down automatically switch over to the other one automatically. Please only apply if you already have worked with PFsense before and if you are able to deliver as per our requirements.