There's a paid version ($1.99) but I couldn't find any info on what the "upgrade" adds. My wife uses the app dozens of times a day to keep her ukulele in tune. It works better than the clip on tuner she used before the Pano Tuner app.
The app works on any instrument. If a band has someone playing a non-tuneable instrument (for example, a xylophone or an old piano with old strings) that is not tuned to A-440, You can record the xylophone/piano playing what should be an A-440 and the app will set its A to the same freq as the xylophone/piano. Then the rest of the band can use the tuner to tune their instruments to match the xylophone/piano.
Pretty cool app!