For the UK I use three:
- Weather Pro from Meteogroup (they're the ones behind www.raintoday.co.uk).Their forecasts are value added not just vanilla model output. It has weather, radar and satellite for Europe.
- Rain Alarm for quick radar and rainfall notifications.
- Short cuts to the UKMO website.
I did try some of the apps that scrape the UKMO website, but found it as a quick and easier to use the bookmarks.