Radioactivity Counter

★★★★★ I compared the readings from this app to my GMC-300E Geiger counter and the readings were accurate within a margin of error +/- .003 given a top end cpm count of 2000 or 50 mR/h. I duplicated these results 12 times over 3 hours. I took the advice of other users and placed 2 black duct tape strips over the camera, so only gamma rays could penetrate to affect the sensors. This is very accurate, and I would absolutely recommend this product.

★★★★★ It Works! I have worked in the nuclear energy field for 25 years, with a specialty in radiation protection. I initially laughed at the idea of a smartphone being used to detect and measure radiation. I was wrong! Although this doesn't respond in the same range as your typical "Geiger" counter, it does respond to radiation linearly at levels greater than approximately 2 mrem/hr (100x average background) to 200 mrem/hr. Most people do not have access to rad sources, so many will probably assume that it doesn't work.

★★☆☆☆ Didn't work on Nexus 4, no reply to emails I bought the $4+ app, and installed it to a Nexus 4 with the back lens cover covered with 2 pieces of black electrical tape. I borrowed a real Geiger counter and some radioactive samples that read about 10-20x above background when very close to the sensor. One was tested even though a thin metal lid with both this app (and nexus 4) as well as the real Geiger counter. After following the instructions and allowing the app to calibrate, it settled on a background count around 20 (I tried it several times, and it was roughly 20 each time). The app does mention something about a 60-minute test but no amount of searching would allow me to figure out how to change that time. After calibrating (~20), tried detecting the samples. What would normally take the Geiger counter from ~20 cpm to ~500 cpm took this app from 20 up to 26. It is barely statistically significant. Reviewed the website, noting I should have had more than enough sensitivity to detect this. After failing to get useful results, I sent 2 emails to the developer from their site. Their site asks you to email them before you give them a one-star rating. After no reply in 2+ wks. (still nothing) I rated.