There is no IPC going on in this case.  IPC occurs once when the simulator is started, and the resulting coordinates are stored within prosthesis as the initial latitude and initial longitude.  The timer is used in this case for calls to navigation.geolocation.watchPosition, to query the current latitude and longitude, which may differ from the initial coordinates if the user chooses mock coordinates.  This allows you to change the coordinates being reported as the position is being watched.  I agree that hard coding the interval is not the best thing to do, but in future iterations on this code, it would be nice to allow the developer to change this.