iPhone Live Weather App
While not strictly an app in its purest sense, using various meta tags it runs full screen in Safari once added to the home screen and includes an icon, making it as close to an app as you can get. Indeed using meta tags is a quick and easy way to get the 'app look' while not having to go through the iTunes store.
The data refreshes every 3 seconds via our offices in Central London, the weather station is located on a roof just off Tottenham Court Road.
Simply go to http://www.casa.ucl.ac.uk/weather/iphone.html and then click the + icon to 'Add to Home Screen' on your phone. The page is formatted to work with the majority of mobile devices so if your not an iPhone user you can still get the live updates.
At the moment only London is available but if there is interest we will make the template available for other users and locations :)