Assumption: Cell-phones generate some degree of electro-magnetic radiation. Whether it's harmful or not is not the question here.

Claim: Certain devices may "neutralize" this radiation. (Ex: http://www.giawellness.com/2/products/terra-gia/cell-guard/)

Questions:

• Is such a claim even physically possible with what is known today (in stick-on form, as advertized)?
• Presumably a full case made out of special material could limit it.. What effect would a suitable case have on the call quality and/or wifi connectivity?

(Related Question: Could cell-phone radiation cause cancer?)