the Fitbit mobile app
With this app, you can get always the current UV index of your location. It shows you additionally if you should use sun cream to protect your skin from the UV.
Please note: In order of financing the access to the data for the UV index, the app will cost 2.00 CHF and has to be purchased via the schmuckli.net Store.
If you want to improve the translations of the app for your language, you can contribute to the translation project here: https://poeditor.com/join/project/xybqXydgS8