Motorola M900 User Manual page 111

Do wireless phone accessories that claim to shield the head
from RF radiation work?
Since there are no known risks from exposure to RF emissions from wireless
phones, there is no reason to believe that accessories that claim to shield the
head from those emissions reduce risks. Some products that claim to shield the
user from RF absorption use special phone cases, while others involve nothing
more than a metallic accessory attached to the phone. Studies have shown
that these products generally do not work as advertised. Unlike "hand-free"
kits, these so-called "shields" may interfere with proper operation of the phone.
The phone may be forced to boost its power to compensate, leading to an
increase in RF absorption. In February 2002,the Federal Trade Commission
(FTC) charged two companies that sold devices that claimed to protect
wireless phone users from radiation with making false and unsubstantiated
claims. According to FTC, these defendants lacked a reasonable basis to
substantiate their claim.
Consumer Information on Wireless Phones 103 English