Counting rejected measurements

Hi all,

When using OutlierFilter, one may want to check how many measurements were actually rejected via the Status in EstimatedMeasurement.
With the Batch Least Square estimator, one can call getLastEstimation and iterate through the map values.
What about Kalman filters? The only way I see would be to set up a custom KalmanObserver. Am I missing something? If not it would be nice to have such an observer natively.