I have been working on IMU sensors to get orientation and I am looking for an open source EKF filter! Or please share ur expertise if anyone has experience!
I took on the same task this summer with a flight-path interpreter. Check out my implementation of the linear filter here.
It looks like researchers believe the EKF yields less reliable estimates without some complicated mitagtion techniques. For measurement that are changing very rapidly (unlike GPS navigation where EKF is indeed a de facto standard), consider avoiding the EKF. According to that paper, the ongoing-estimate can diverge pretty quickly.