Here's a little about what the cell phone signal does to human neural tissue:
http://www.eurekalert.org/pub_releases/2006-06/jws-cpe061906.php
Here's the bad news about the most recent research;
http://www.news.com.au/sundaymail/story/0,,21092445-5003419,00.html
http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2007/01/25/nmobile25.xml