Android Voice Changer App While Calling

I'm looking for someone who can make a Voice Changer app for Android phones. The hard part is that it has to change your voice WHILE making a phone call. - So either it is a running app on the background on the phone which does this or - You modify the open source android "dailer" app in such a way that it changes your voice when you speak. The dailer app can be found on multiple websites. (This solution probably only working for outgoing calls only) I don't know if above is possible and whether there is a better solution for making a app like this, but i'm off course open for suggestions. App must also have extra functions as record call etc, but these extra details will follow. First i want to know if someone can tackle the main function "voice change while placing a call" High graphical design is not neccesary, although it must have some basic design and layout.