The images on the following URLs show GPS tracks obtained using OSMTrack on iPhone4S. I get these tracks on the train (Yamanote-line) in Tokyo.
It is strange that some part of the tracks seems to follow the road, instead of railways. I suspect that GPS data on iOS might refer road data (but not railways) of Apple Map and tries to snap on the nearest road when it is moving fast enough.
How do you think? Please try with your iPhone, if you have.
If my speculation is true, OSMTack on iPhone is no longer suit for OSM mapping.