Can the iPhone determine if you\'re facing north, south, east or west?
I'm not so sure, but here are some options:
Gather two or more data points over 3-10 seconds. Plot out, with GPS, where the motion is tending towards. That could be your direction.
Also, you could use the accelerometer to determine which direction (left, right, forwards, backwards) the iPhone itself is moving. Pair this up with the previous data, and you may have a more accurate reading.
These aren't great, because GPS isn't as sensitive as you'd like, and Accelerometers are probably more sensitive than you'd like, and both depend on motion. But they may work.