My brother plans on using it for DJing with Traktor.

The ideas is that you never ever need to touch a laptop while DJing. I would love to extend it to use an android phone as a display (so that the laptop can be hidden away under the table or whatever).

At the moment, we have 4 banks which change the MIDI channel of everything else, and 4 banks for the 16 midifighter buttons. These four banks basically map to each one of four Traktor decks. The 4 "global" banks are then used to choose between browsing through songs, loops, various deck control commands and effects.

I imagine mashing up breakbeats with those buttons would be really compulsive :)

Its addictive to mash the buttons and see what happens :D Even an unmodded midifighter provides hours of fun, even if (like me and unlike my brother) you're not terribly musical.

Anyway, we had a little setback - think we may have fried the atmel mcu.. :'( but once its all finished and cleaned up, I intend on releasing the code and writing a blog post about it, which I'll probably submit to HN.

You should submit to http://hackaday.com as well. They'd most likely feature it.

Also, have you heard of http://hexler.net/touchosc ? It's brilliant fun on the ipad, I've never tried it on android, but there is a port.

Touchosc looks interesting too, I'll have to give it a try.