Knölli is a free iPhone app developed by Jens Sundermann that allows users to report illegal parking within 30 seconds. With just a few photos of the vehicle and some necessary information, users can quickly send a pre-generated email through the app.

The app automatically works in Berlin, Böblingen, Braunschweig, Dortmund, Düsseldorf, Erfurt, Hamburg, Münster, Potsdam, Saarbrücken, Stuttgart, and Wuppertal, using the respective city's email address for the local traffic authorities. For cities outside this list, users can manually enter the email address of the local traffic authorities if needed.

Knölli is a convenient tool for anyone frustrated with blocked sidewalks and bike lanes. It simplifies the process of reporting parking violations, making it easy for users to take action and contribute to safer and more accessible streets.