djay 2 for iOS
djay is an Apple Design Award-winning app that turns your iPhone, iPod touch or iPad into a full DJ booth, with manual mix modes, music library integration and more.
The new version adds "HD Waveforms," a new tool that allows users to touch and interact with their music in an all-new way. The waveforms are color-coded and extremely accurate, making it easy to touch and edit songs easily, even on a small screen.
The iPad version is $4.99, with the iPhone version is just a buck. These are launch sales prices, and will double soon.