The iMaschine app is like having a music studio in your pocket | DVICE.
This app looks fascinating. In this video it is used in an electro-pop context, but what are the possible uses for instrumentalists? Is the mic on the phone good enough to pick up and loop effectively a trombone? There are some add-on microphones available for iOS devices so, perhaps, that would increase the effectiveness of such an app. This could be a great, low-cost ($4.99) entry into the loop machine market for those interested in looping content.
Native Instruments website
University of Iowa Trombone Studio 