We had the rust evader on our van. Ive heard theories debating both ways. Some say it works, some say no. I for one say that It seemed to help, but I can't prove it. I dident have any rust on the van till a while after I took it off, but that may just have been timing.
I woulden't pay much for one. Your money, like Kenny said, is better spent on proper preperation during a restore. But if you're not doing a full paint or body job, then the electronic gizmo is an option.
It definatly won't hurt anything to put it on there.
Give me some time and I can probably come up with a used unit for you, for the cost of shipping.