Not sure if this answers your question but I have some magnets installed on the water main coming into my house and also around the pipes entering and exiting my water heater. I also have them on my shower head. I figured I would maximize the benefits this way. There is a difference but not like a water softener where it feels slimy or hard to get the soap off. To me the difference is my usually hard water doesn't hurt anymore when I turn the shower on. The effect is more subtle, but yes magnets really do something to the water. Here is one from ebay, you will find many others like it if you search.

http://cgi.ebay.com/Magnetic-Health-Water-Treatment-Softener-System-Magnet_W0...

and

http://www.magnet4less.com/product_info.php?products_id=699