As io mentioned Teamviewer works on iPad and iPhone and Windows with vvvv. I’ve used it and tested patches it works smoothly; the only problem is some of the keyboard and mouse steps for instance the middle mouse click for vvvv menu etc, but it is easy to use it to have a full screen vvvv display in real-time with very minimal lag, the iPad shows whatever the PC is showing on its desktop and you can control vvvv or any program from the iPad using your finger touch.
Yes iDisplay is good for local (through wifi) setup. It is great to have an extended monitor for controlling GUIs, it is fast too. The same company makes RDM+ Remote Desktop for Mac and Windows which is like Teamviewer: