If you know what this is, BUY IT!
Extremely handy tool for the audio folks, an RTA in your pocket. iPhone is somewhat limiting at a mere 105dB max and noisefloor of 28dB on my phone but for most basic quick tweaks, this will do the job. Of course if you get a real mic, this app is priceless. So Nathan and Luke, stop reading this and buy it already :)
Im a freakin App junkie! about
RTA