Sites and apps similar to Radmon.org include Geiger Counter World Map, which is free and open source. Other options are Safecast Map.
It is developed by GQ Electronics. Its devices (e.g., geiger counters) are fully compatible with the website and it is very easy to track and upload data of the levels of (ionizing) radiation, including radon.
United States
Safecast is an international volunteer driven non-profit organization whose goal is to create useful, accessible, and granular environmental data including ionizing radiation. All Safecast data is published, free of charge, into the public domain under a CC0 designation.
