Instead of using the GammaPix app, the group in Idaho, led by researcher Joshua Cogliati, developed their own app called CellRad to find the radiation. Surpisingly, of the phones tested, the Nexus S, a phone launched late in 2010, detected the most radiation per image. The Samsung Galaxy S III produced too much noise, according to the researchers. And there was less variation between two Nexus S units than between two units of the other phones tested.
Speaking of which, the other phones involved in the testing besides the Nexus S and the Samsung Galaxy S III, included the Samsung Galaxy Nexus and the Nexus 4. Because of the much higher resolution on the back snapper, it was employed for the test instead of the front facing camera on each device. The test used the CellRad app to check for isotopes of Selenium, Iridium, Caesium, Cobalt and Americium.
The guys in the lab did say that despite this capability, a smartphone will never replace a Geiger Counter in terms of the quality of radiation detection.
source: Arxiv.org via TheRegister