ParkenDD is an app that can display and display free parking spaces  in real time  on a map. Now also - to Dresden and Ingoldstadt - for Zurich.The special thing about it is that all the data that the app uses are freely available. The data is collected and processed via an interface to the app. All these components, the interface, the software for editing the data and of course the app itself are free  and can be used and adapted by anyone.