Dual WANS

[amd.64]

I need to set up dual WANS on multiple routers.

I found this Multi WAN.

Is this the best tutorial to use
If it is the best, what is the point of the monitor IPs. I get what they are (going by the name anyway, maybe they aren't what I think), what is their purpose for dual wans? IE why are they need for a multi WAN setup but not a single WAN setup?
If this is not the best tutorial, what is?