Link: iAmADalek (Doctor Who) for iPhone, iPod touch, and iPad on the iTunes App Store
This will record your voice and play back what you have said using a 'Dalek-Like' voice.
Note: The app is not available from Apple's UK store but it will offer to switch store so that you can link to the US stores to download the app.
Requirements: Compatible with iPhone, iPod touch, and iPad. Requires iOS 3.2 or later.