iPhone OS 3.0 tested
Theater Tool allows you to calibrate your home theater speaker levels without purchasing a Sound Pressure Level (SPL) meter like RadioShack's 33-2055 or 33-4050 which can cost more than $40. Turn on the pink-noise generator in your receiver or amp, lock a reference level in the tool, zoom in on it and set the other speakers to match.
The application also includes a distance/delay calculator to assist in setting an appropriate delay time between front and rear speakers.
This application requires an iPhone or suitable microphone for an iPod Touch.