Sometimes you've got the T-Shirt, but this app makes me want to buy the jacket ...

I don't have the jacket, but just taking a look at this app makes me want to get it already. I actually know someone who is in fact testing this out, so I might get a play at some point.

It does look like a lot of fun ...

Here's the app's description:

The MIDI app allows you to setup a basic musical set which you can easily fiddle with, without having the need to know anything about music. Just open the app and play as you feel it.

To use, first select a section by placing touching one of the red circles above the jacket’s illustration. Each can hold a different sample and volume, that can be selected from a list, and easily activated by pressing play.

Nervs work a bit different. They hold a control grid that you can use to modify the preset effect filters, in order to alter the sample.

MIDI app can become a powerful tool if you add in a MIDI jacket. Just connect your iPad to the MIDI jacket’s WiFi server and start using OSC messages to wirelessly play music on your app. The application is configured to work along with the jacket right out of the box.

The app is free, the jacket, probably not I'm thinking.