I used the BinaxNow test to return back to the US today. Unfortunately did not transit through Germany.
But a couple of points about the Navica app:
1) It calculates the days since the negative test differently as compared to the CDC. Normally a negative test within 3 days is allowed. The Navica app starts counting 1 day earlier. So in this case you might be better off with a print out instead of showing the App
2) The share function for negative results on Navica doesn't seem to work properly from an iPad version of Navica. Works much better in the iPhone version. I couldn't get it to share the results from my iPad properly