By now, there are already quite a few iPad controller for Ableton Live. Conductr, now in the App Store, has taken up the cause to be made specifically for live performance. And that in a very sleek and minimal design.
Conductr works as a modular system shipping with three modules - Clips Module, Mixer Module and Master Module - as well as User Modules. These can be combined in four different display modes with 4, 3 , 2 or 1 modules shown on the screen, which can also be changed on the fly. The idea is that you create a separate project in Conductr for each Live Set in Ableton Live.