TouchOSC is an app that turns your iPad into a modular control surface. It uses Open Sound Control (OSC) to communicate with compatible DAW’s and software via WIFI.
Setting up the app can be a bit tricky, but they do have some documentation and installation help available. Once installed, you have complete control over the program you’re communicating with. For example, when synced to a DAW, you can adjust track levels, inserts and effects, pan information and much more.