Possible to have two failover networks?

Hi All... Is it possible to have two failover networks? I haven't found any mention of it, which makes me think it's not possible, but as we had an issue recently where someone took down a link in our network failover causing both devices in our HA pair to become active I thought I'd check in with some experts :)

The units are physically separated, which rules out a hardware failover connection.

The network failover behaves as expected, but I'm not sure if there is a way to guard against the actual failover network falling over. In a perfect world I'd send a heartbeat over a couple interfaces, and if the standby unit didn't hear a heatbeat on the primary failover interface it'd then listen on the secondary interface before deciding things had gone bad and becoming active.

Am I missing something, or is a single failover network the only way to do things?

Thanks Simon