There's another site that took one apart. I can't post a link, but it made for a good laugh.
The magnets are about the size of watch batteries. The theory of using magnets for watersoftening is a valid theory. Eco-Aqualizer's claims are far from valid however.
If you want to do it in your tank order some rare earth magnets and duct tape them to your PVC pipe before it goes to the skimmer.
This and a UV are two totally different things however. Depending on what you're looking to do there are many ways to improve a tank. If you're thinking about UV, I run one and love it. I don't think they're a necessity, but I do think once you run one you'll be pretty happy with it.