New Scientist reports that the peripheral has eight photodiode sensors to detect radiation and aluminum foil to screen alpha and beta particles. Second generation peripherals, known as Pokega Type2, do away with the need for batteries, using the connected iPhone as a power supply.
The app functions as the Geiger counter display, but also uploads data to a Radiation Watch server where readings are collectively mapped for an overview. Apparently there are over 10,000 users, though the viewing of maps is limited to Radiation Watch members.
The main advantage of the Pocket Geiger appears to be cost. Where a typical personal Geiger counter would cost well into three figures, the peripheral and app cost a mere US$46 - or $65 for the Pokega Type2.
Of course, the WikiSensor app we looked at last October did away with the peripheral entirely.