Use the camera in your Android smartphone to detect radiation with the Radioactivity Counter app from Rolf-Dieter Klein. Just place a small piece of black tape over the camera lens, calibrate for ambient noise, and you’ll be ready to take readings in no time. The app uses the device’s built-in CMOS sensor to detect primary gamma radiation and some higher beta radiation. It’s not as sensitive as an actual Geiger counter, but it does read some common radioactive sources like airport X-Ray machines and certain mushrooms. The app itself was developed in response to the Fukushima Daiichi nuclear disaster. [via Hackaday]