Any self-respecting digital artist these days uses a graphics tablet to pipe pen input into PC applications. The problem is that good graphics tablets like the Wacom Intuos line are pretty spendy. If you've got an Android device lying around and like to use the GIMP image editor on Linux, you've got all you need for a basic graphics tablet setup thanks to a new app.
The XorgTablet app and driver developed by the gimpusers.com team allow you to select your Android tablet as an input device in GIMP. You may be thinking that sounds interesting but limited – after all, graphics tablets are useful because of the pressure sensitivity, and capacitive screens don't have that. Well, Samsung was good enough to license Wacom's pressure-sensitive pen technology for the Note devices. In the video you can see a Note 10.1 used as a full graphics tablet complete with pressure sensitivity. Other devices will work, but won't be as useful.
The app can connect to your PC via a cable, or over WiFi if you're set up correctly. When you enable the Android device input, the mouse will stop relaying commands to GIMP, so it's not completely ideal. Also, this is Linux only due to the X.org driver. You should be able to use the XorgTablet app in any program on the PC, but there aren't a ton of Linux programs that would benefit.