Voice TwisterTM Autotune App
 

I have yet to come across an autotune app for PPC, but this is along the same line and the closest I found:
Voice TwisterTM is the first professional application that gives you the power to morph your voice on a Windows Mobile device.

The easy to use voice selection will have your friends and family laughing as your voice is converted to a Space Squirrel, or your kids are talking like a Giant at story time. Choose from the many preset voices, or you can use Tweak and Speak to change the pitch and add an effect, creating a unique voice of your own.

In addition to live voice changing, Voice Twister can play an existing audio file in the morphed voice, and save it to a new file. You can also record and save your live voice for play back later.