CanViz

CanViz mirrors one of your Windows screens on your mobile device and sends the input of the device back as mouse or touch input if supported.

This allows to use most graphic applications on your PC using a stylus or even your fingers on your tablet/phone.

While this tool currently might not be as elaborate as duet-display or astropad, it certainly is cheaper currently and does not modify your system in any way (it does not install drivers or whatever to make the app work)

You should have a pretty stable w-lan ... or just use usb which is advised anyways.

As the project is kind of in a very early stage, nothing should be expected to work at all. It has been tested with a few applications and seems to be kind of usable, but don't expect a wacom replacement for cheap or anything.