German electronica pioneers Mouse On Mars have their own audio effects app, WretchUp. Presently it only works in rjdj on one iPhone, but they want to turn what they've learned into a standalone, open-source, app. In order to do that, they are soliciting donations on indiegogo. I don't like to post stuff for indiegogo and Kickstarter, because there is zero accountability and well meaning people are getting burned. This project however, is promising nothing, so you are sure to get what you pay for!
Here's a demo of what they've got so far.