I have an app called dB, which uses the iPhone mic. Shows SPL with four curve options. It assured my tweeters were not blown. I might have mentioned I’m old, and not the best judge of high end.Not automatically as yet in this first version, but means to avoid it have been discussed in the forum and WiiM are very open to feature requests to improve their software.
Why not? The respected HouseCurve app does as well, and the characteristics of iPhone mics seem to be well understood.