Aftermarket rear defroster questions

Looking at rear defroster options.

Anyone have any experience with these guys?
http://www.frostfighter.com/clear-view-defroster-order-guide.htm

I don't have the rear blower unfortunately.

I do keep this car garaged, but I have noticed that it does fog up a little when it gets a little cooler outside and starts to rain. Especially when I drive it around.

Of course I do see these little defroster heaters they sell that plugs in to your cig. lighter. I can probably use that as a temporary option.