Best reading for the headwind component ist IAS vs ground speed, especially on ridge or wave where no circles are flown. Also usefull on long final glides with no circles.

That is actually mathematically incorrect. You can't determine the headwind component from just the ground track and the airspeed by simply taking the difference between both...

XCSoar however uses a more advanced algorithm that gets around that limitation if you connect it to a glide computer that sends TAS/IAS to the device. It is using a Kalman filter designed by John Wharington, that works pretty well and gives you accurate wind information within a short time of flying..