PIA - What's the proper way to do gateway monitoring?

[Finger79]

I currently disable gateway monitoring for the PIA gateway since it doesn't respond to ping.  Is there an alternate address that one can enter in the "Monitor IP" field?

[TomT]

I read somewhere you can add any pingable address.
If you get a response you know the VPN is up.

I've added 8.8.8.8 to mine and my PIA shows online

[AndrewZ]

pfSense will add a static route for the monitoring IP via the given interface.
If there is a x.x.x.x address is used there then the router will always send traffic for that IP to PIA, adding latency for non-VPN users and breaking Geo lookup (in DNS case).
I'm using there one of Level 3 DNS resolvers (4.2.2.1 - 4.2.2.6)  which I don't need to contact for any other purpose.