DAW Remote HD can be configured as a unit in a control surface group.
For instance, if you have two iPads with DAW Remote HD, or one iPad and one Hardware Control Surface. You can configure one to control 1-8 channels and another to control 9-16 channels.
For instance, Apple Logic
Open Control surface setup window. When two controllers are both in the one rectangle, they are configured as a control surface group. If you want to make them work in parallel, just drag one of them out of the rectangle.
In group mode:
In parallel mode: