Apps for everything!
Rolf-Dieter Klein has developed an app to turn an android phone into a radiation counter. Here are some videos of how it works. The camera lens is blocked from light, and the camera sensor picks up the radiation.
The app was tested on several phones at the Helmholtz Research Center in Munich, on radiation sources ranging from 2-10 µGy/h up to 10 Gy/h (about 10Sv/h). The video shows nicely how the radiation affects the camera sensor.
The calibration procedure seems difficult to me, but Klein says that this is being improved.
H/T to @adamrofer for last night’s tweet about the android app.