Parkulator App shows car park fees calculated from the timings you set and lot availability (when available) in Singapore. It is an internal project that started two years ago and revived recently for a Data.gov.sg competition for apps that use government data.
The first step was finding out when and where users would use such an app. We introduced colleagues who were not involved in the project the general premise of the app and how it could save them money and asked a few questions. This helped us understand at which points our product will be most useful, and prioritise features accordingly.
The simplest way would be to start the app directly with the map and the user's current location and put a search bar on top. However, very few users plan (or don't plan) their trips this way, and would prefer to enter their destination first. Once they select a building or area, the map loads and the Timing Menu is open to ask them to input their start and end times.
A Find Nearby button is still available for those who do use the app on the last minute or want to look nearby.
A user can just pan around the map if he decides to park farther away. Zooming out to a certain level will collapse the priceboards into pins to provide a cleaner view.
Changing the timings is easy for users with flexible times. Just open the Timing Menu, adjust the times and close it, and the priceboards will update on the map.
Some early wireframes with a pen and some dot grid paper:
See the app on getparkulator.com (Android only for now, iOS7 soon)