We read about them! Very cool project, especially from high-school students. A lot of people got onto this idea about the same time. See also CellRAD, which is

We read about them! Very cool project, especially from high-school students. A lot of people got onto this idea about the same time. See also CellRAD, which is an app that is supposed to act as a dosimiter to detect when you are near radioactive sources. It's been known for quite a while that silicon pixels can detect ionizing radiation (in fact, that's why we use pixel detectors in the inner tracker layers of state-of-the-art particle detectors such as ATLAS and CMS). The problem with the pixels in the CMOS camera of your smartphone is that they are very small (in both pitch and depth) and were optimized to respond to optical photons, rather than charged particles. We have played around a bit with implementing these radiation-sensing features, but the main goal for the CRAYFIS project (and which sets it apart from other similar projects) is to create a distributed network of phones that all work together to act as a giant telescope for UHECR events.