Dan Trueman has ported his Mac OSX app bitKlavier to iPad! This app provides samples of a "prepared" digital piano. For those unfamiliar with the term, a "prepared piano" means someone put weird shit on the on the strings. This app has similar caltrops sprinkled throughout the digital piano samples to provide some unexpected results. It doesn't look like Audiobus/IAA made it into v1.0, but it does include MIDI support.
bitKlavier iTunes Description:
bitKlavier is the software that drives the "prepared digital piano;" it has been used by a number of composers for creating new music, and has been featured in performances around the world.
Like the prepared piano, the "prepared digital piano" feels just like a piano under the hands and often sounds like one, but it is full of surprises; instead of bolts and screws stuck between the piano strings, virtual machines of various sorts adorn the virtual strings of the digital piano, transforming it into an instrument that pushes back, sometimes like a metronome, other times like a recording played backwards. The virtual strings also tighten and loosen on the fly, dynamically tuning in response to what is played.
To begin, load a sample set ("lite" will load quickly and on older iPads, "medium" sounds better, but takes longer to load) and experiment with the included presets, many of which are from existing pieces (the Nostalgic Synchronic Etudes by Dan Trueman, and the Mikroetudes, a collection of small pieces by various composers), others are examples for exploring the various types of digital preparations. Work with the on-screen keyboards, or hook up a USB-MIDI keyboard using a Lighting-USB adaptor and play with a full-sized keyboard.
Dan posted an excellent explanation of the app, and what weirdness awaits within. Unfortunately the audio is from the camera mic, so you can't get a sense for how the app actually sounds.