Groovy Pianotuner

Great for guitars also. God for setting intonation

Works for guitar too

In a dead silent room the wheel was spinning outta control!!!!, I tuned a note middle C dead accurate with a full size strobe then attempted to use this app to see how well it performed. This app is useless. Except if you like watching the pretty interesting visual effect of the never ending black and white hashes

It’s a Free Strobo Tuner that works well.

This app only works with inner cell phone microphones. It won’t work with the dongle (iPhone 8) - it immediately freezes. Needs more work.