InsTuner Chromatic iOS Tuner
InsTuner is a chromatic tuner on iPhone & iPad which supports Fine-Tune, Instant-Tune FFT and STFT mode.
It's free until July 21st.
A "Fixed Tuning Wheel" helps you find the position of your current pitch.
The company says that the system helps you tune your instruments with a precision of ±0.1 cent.
You can find it for iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation), iPod touch (4th generation) and iPad on the iTunes App Store.