Great initiative.
I think one useful feature will be to automatically show on app startup all stations close to user’s position, so the app would be as informative as possible. Also stats on radiation trends and a few lines on exposure limits and their effects, as published in current literature.
Email alerts or push notifications should be configured on the website, and delivered to the mobile apps, for events like: major changes in background radiation levels at some location, preconfigured threshold reached, etc.
The ui should take advantage of modern UI/UX