[hagcam]

http://www.dyersonline.com/progressive-i...ystem.html

I had to replace mine this past year. I went with a portable for a couple reasons. These carry a lifetime warrantee if the fail you mail them back and they repair them. If you use the hardwired version they mail you a new board and you replace it, or I guess you would have to pay somebody to replace it.
My understanding is that these devices do not like generator power, so you have to wire them in on the shore power line. I figured that it was just easier to use a portable version.
The link above was the best price I could find. A few years ago the Wanderlodge group arranged a group buy and got the EMS for even slightly less from this supplier. It is a good price as is, and was highly recommended to me.