I used the Touch.AngleForID() expression and it doesn't generated useful values all the time, as described in the manual: <font color=blue>"A touch must be moving across the device screen for this expression to contain a useful value."</font>
So I decided to build my own Touch.Angle expression and was amazed (thanks to the math.angle() expression) how easy it was.
You just have to get the starting & ending Touchs X and Y and put it in math.angle() like this:
angle(TouchStartX, TouchStartY, TouchEndX, TouchEndY) and you'll always get a correct and useful angle for your touch.
And finally here's a little example (you can even use mouse to test):
Hope this helps somebody.