Scott, from scottandmichelle.net, figured out how to detect which way the nav sensor was being moved. I did some further investigation with the data output and managed to figure the rotation per second readings that were also being returned with it.
The new HTCNavSensor has a single event:
This event fires whenever the Nav sensor event is detected. The rotation event will provide the user with an approximate rotation per second value and a radial delta. The radial delta is a double value that describes how much the user has moved along the nav sensor since the last time the event was fired. I.e, a radial delta value of .25 would mean that the user moved his finger around a quarter rotation since the last the last time the nav sensor event fired.
As usual, the updated API can be downloaded here. The other sensor APIs (accelerometer and light sensor) are also available in the same zip file. So that wraps up accessing all the different sensors on the HTC Touch Diamond!
Let me know if you find any bugs!
Edit: I found a bug where the nav sensor was reporting clockwise movement when actually moving clockwise. Fixed that. Also updated the Nav Sensor Test to show a red line that rotates as you rotate around the sensor.