Iphone App for tuning your system in the room

What Iphone apps have you used to adjust speaker placement and other acoustics in the room.
the SpectrumAnalyzer from ONYX Labs is a pretty good real time analyzer. You should also look into getting a better mic for the iPhone as the inbuilt mike has some known deviations. 

Overall however i find these apps as more helpful confirmatory tools then actually proscriptive and get better results from careful alignment of geometry (using lasers for alignment to ensure each speaker is aligned relative to the listening position to within <1mm tolerances) and use of a test tool such as the ASC MATT disc
Try audiotools app. Free SPL and RTA meter, and a lot of others that are not free.