There was also this one, a bit earlier, "Observing Ultra-High Energy Cosmic Rays with Smartphones". https://arxiv.org/abs/1410.2895 https://arxiv.org/abs/1410.

There was also this one, a bit earlier, "Observing Ultra-High Energy Cosmic Rays with Smartphones". https://arxiv.org/abs/1410.2895 https://arxiv.org/abs/1410.2895 I (thought I) signed up to be informed of beta releases, but never heard anything. I just checked their website[0] and it mentions a beta app, but that seems to just go to a signup page. [0] https://crayfis.io https://crayfis.io