Detecting something hitting iPhone screen

I wanted to see if the brainiacs 开发者_开发问答on this site could help me figure out a way to tell if something hit the iphone screen, not a finger but an object. My initial though was the accelerometer but dropping the object on the screen doesn't register on the accelerometer graph sample code and the iphone would be moving in any case, which would swamp out the signature of the hit. I can't give too many specifics but it's a light object and it makes a definite click sound when it hits the screen. So I though of FFT on the audio. The problem is the object makes the same sound if you miss and the object hits the ground, which the iPhone can defintely hear. Does anyone have any ideas? Ok, what the hell, it's a ping pong ball and you can guess what I'm trying to do. Thanks.

The capacitive touch-sensitive technology only works with things that can act as a conductor, and complete a circuit. In the case of your fingers, your body actually serves this purpose.

"Touch" sensitive should not be confused with "pressure" sensitive. The iPhone/iPod/iPad is not pressure sensitive.

You'd be on the right track with using the accelerometer, but only if the object hitting the phone (anywhere, screen or not) actually caused the phone to physically move.

More info: http://en.wikipedia.org/wiki/Touchscreen#Capacitive