RTA Lite is pretty useful, but it will not serve as substitute for a calibrated microphone and a good PC based measurement suite. No stand alone app that uses the internal mic in the iPhone will be very accurate. The mic and the programing that makes the mic suitable for voice pickup outdoors conflicts with the need for the mic to have a flat response in the bass region. The programing is non-defeatable.
RTA Lite has accuracy issues in the bass portion of the audio spectrum for the aforementioned reasons. It is difficult to get consistent measurements below 200Hz. If you check my galleries you can see a couple of screen shots of measurements of my system at the listening position using pink noise and RTA-Lite. It will tell you about big problems but you will probably not see smaller ones due to a lack of resolution.
Scotty
