My husband downloaded this nifty app on his DROID smart phone for FREE to test the pitch of any instrument. You simply play at note and it will tell you how close to actual pitch the notes are by a “needle,” letting you know what pitch it registers as and what direction it is off in (if it is higher or lower than than actual perfect middle C for example).
It is too cooI, just got finished testing both of our xylophones.
I am sure there is something similar out there for the IPhone.