It is known that the EM radiation from GSM phones is not
enough to ionize DNA. A recent study on 400 thousand GSM subscribers in Denmark confirmed that. The main reason that most consumer electronic devices react to GSM phones receiving or sending is that most of them contain poorly designed amplifiers (from an electromagnetic compatability viewpoint). The amplifiers are sensitive to stuff way outside their operating range. In many cases this can ofcourse not be helped. The reason is not that the GSM handset is "SO POWERFUL!" as many like think and use as arguments.
The maximum transmission power of a handheld GSM phone is 2W. Thats probably less than your flashlight. People have been using much more powerful handheld walkie talkies for a really long time. HAM radio operators often work with 100W not to far from their head.