MobMuPlat (short for Mobile Music Platform) lets you create your own custom audio software for iOS, via the open-source audio environment PureData.
MobMuPlat hosts a list of user-created documents, each of which defines a user interface and audio engine. MobMuPlat can do synthesis, sampling, networking via local wifi, OSC messaging, query and set hardware characteristics, display images/graphics, and much more.
see www.mobmuplat.com for more info.
Creating your own work consists of two parts, both done on your laptop/desktop.
First, create the audio engine using the graphical programming language Pure Data (PD)
Second, either use the native PureData GUI, or create a graphical user interface (GUI) with the MobMuPlat Editor.
With PureData and the MobMuPlat Editor open, and data sent between the two, you can simulate the app behavior on your laptop/desktop. Once development is complete, just drag the two saved files into the "Documents" folder of iTunes, and they are uploaded to your device and can be opened in the MobMuPlat app...
Download these tools from www.mobmuplat.com