Thanks for the link, @frog, I was really wondering what it was about. IF one already has some iThing AND if one wants to go from zero to a full six-pack THEN it seems like a nice idea. As a secondary or back-up, it feels like pricey. And not all are required: compass functionality is offered by any satellite based navigation app (with the sun also available, mostly) , and AoA is not normally needed, except (as discussed not very long ago) in certain high performance planes.