That Vindriktning thing is quite interesting.
I grabbed myself one approx. two months ago an now combined it with a Wemos D1 Mini and a BME280 breakout board to make some sort of outdoor weather station.
I really dont know how accurate the Sensor is (have nothing to compare), i modified it with some hoods so that the air will be sucked in from outside of the case and will go back outside when it passed the sensor.
We will so how it works out in the next couple of months.
I documented it a bit more in detail on my blog (unfortunately not translated yet but many pictures):
https://blog.sengotta.net/ikea-vindriktning-wetterstation/