Collecting Cell IDs
CellHunter ist available in German and English. By playing the game a joint database is build and extended, that maps GSM cells IDs to GPS coordinates. The generated database is public under the creative commons license.
Objective of the generated database
In buildings you are normally not able to receive GPS satellite data, but your mobile phone (resp. freerunner) might be able to connect to a GSM transmitter. This information signal strength and cell ID of GSM transmitter can be used to retrieve rough GPS data for your phone even your phone does not have a GPS receiver. Freerunner as mobile phone has a GPS receiver and so GSM and GPS position and so it is perfect for building up the database.