I have been a luthier for 30 years and have been using my Stroboconn for that long. I wanted something equivalent and portable. I wrote my first spectrum analyzer (FFT) for hardware I made in 1984 running on a Mac+. I have a lot of expectations when it comes to this software. With in app purchases I had to spend $30 to replace the mechanical strobe which seems expensive for an app. It does, however, function very well. Make sure to calibrate it. I also spent an extra $10 for having the spectrum features replacing my Mac+. (Well worth it.)
I would really like a power meter feature. Beyond tuning I often need to measure string to string balance in piezo pickups. The other feature I would love to have is a waterfall display of the spectrum. It would be an easy add.