Studio Six Digital makes iPhone and iPad sound measurement Apps and hardware. Some of the tools include a SPL Meter, FFT Analysis, Impulse Response Recorder, THD+n Measurement and a Speaker Polarity/Distortion tests. There’s also an Impedance Meter and an Impedance Sweep test.
“The Impulse Response module for AudioTools provides an easy way to capture an IR audio file on the iPhone / Touch, and also calculates the most-needed metrics from the data. Impulse Response is an iPhone port of a powerful mathematical model developed on desktop computers by Daniel Valente, Ph.D Architectural Acoustics, Rensselaer Polytechnic Institute. In seconds, a complete set of measurements is made that describe the acoustic character of a room.” – studiosixdigital.com
There is some competition in this space. Also check out: Faber Acoustical
For more info: studiosixdigital.com