Tawkon an Israeli company developed a mobile phone radiation measurement application that gives users information & tools to avoid mobile phone radiation as much as possible, with minimal disruption to normal phone usage. Once installed, the app provides an indication of the current rate of cellular radiation emitted by the cellphone in-hand.
Tawkon produced a video embedded below in which it clearly demonstrates that when the iPhone 4, Blackberry Bold, and Nexus One are held in the death-grip style, all three handset antennas are impacted. As the video shows, the result is that each of the three handsets compensates for the death-grip's impact by increasing its cellular broadcast levels to a range that Tawkon considers "High".
More Info: Tawkow