The Christan-Wirth-School schedule notifier app for Windows Phone. Better known as CWS Informant, this app helps you to keep track of your lessons. Which'll change, which are cancelled? See it here.
Our school uses the Untis system with web access. The informant is basically pulling this site and doing string operations on it to get the data. Change the URLs in Fetcher.cs according to yur school's Untis web access.