Kaupunkifillarit.fi is an Android application developed by Hannu Leinonen that falls under the Travel & Navigation category. It provides users with a solution to the problem of finding free urban bikes when they are most in need. The app tells you where to find a free city bike, making it the perfect way to get around town.

The application uses information provided by HSL, Fölin, and Oulu traffic on the utilization rate of city bike racks in Helsinki, Espoo, Vantaa, Turku, and Oulu. The data is updated every few minutes, so the number of available bikes may not be completely real-time. However, to ensure bike availability, users can choose a rack with many free bikes. The developers of this app, Sampsa Kuronen, Antero Päärni, Lauri Piispanen, Hannu Leinonen, and Teemu Pöntelin, have provided this service in their spare time. They work at Reactor during the day.