Tracker of buses and trams in Warsaw that uses Warsaw public API for vehicle GPS data and OpenStreetMap for maps.
Easiest way to test it out would be to launch a test server with php -S localhost:8080, then just navigate to that port in your browser. PHP process needs to have permission to write to api/cache directory, as it will cache some of the requests to make the page work faster. Clicking on a marker will select the vehicle and show more information about it. This also allows tracking the vehicle on a map when the data in the API gets updated (usually twice a minute).