With the following code it is possible to setup a button for toggling the setUserTrackingMode in a navigation bar.
// set MKUserTrackingBarButton
// source: http://stackoverflow.com/questions/9876157/is-the-current-location-compass- heading-button-available-in-the-ios-sdk
MKUserTrackingBarButtonItem *buttonItem = [[MKUserTrackingBarButtonItem alloc] initWithMapView:self.mapView];
self.navigationItem.rightBarButtonItem = buttonItem;
// set tracking mode
[self.mapView setShowsUserLocation:YES];
[self.mapView setUserTrackingMode:MKUserTrackingModeFollowWithHeading animated:YES];
How to do this the way (button lower left corner within map) Apple does this in Maps? (Sorry, I'm not allowed to post a picture clarifying it)