As I get ready to do an IPC in a few weeks having not flown for 18 months I wonder how my scan would go on limited panel after reading this post.
Failed the AI in a sim and yep I stared at the AI while the the turn co ordinator showed a steepening bank and the VSI wound down extremely fast. Took a while before getting it to a wings level and finally maintaining attitude. Lost about 2000ft in a short amount of time. Could only imagine what it would be like in cloud and hearing the rushing of the wind.
What I use for backup on an iPhone is to run Xavion the makers of Xplane. It provides an AHRS and will even glide you down to an airport in case of an engine failure. Great for a last line of defence.