The already cool Neyrink V-Control has been updated to version 1.5 and it comes with some cool new features, one of which is V-Window. V-Window now allows you to open up your plug-ins on the iPad and have full control over them - no need for expensive controllers.

Updates in full;

• V-Window - Provides window control for plug-ins, surround panners, and any other windows.
• MultiPanel - New multi-purpose view for a better organized GUI.
• Additional DAW Support - Live, Reason, Reaper, Studio One, FL Studio, Tracktion.
• Logic Improvements - Instrument parameter editing, counter jog/scrub control.
• Pro Tools Improvements - Full-screen surround panner control. Sticky modifier buttons.

I’ve owned this for some months and the previous version was great; now this update makes V-Control an absolute steal. More here