Is is possible to use an android tablet as an extended monitor to my laptop
From the linked article:
IDisplay, the not-so-well loved iOS app to turn a tablet or phone into a secondary display, has come to Android. Now, with this app and an Android tablet or phone (v2.1 or better), you can extend your display.
Sure, use a VNC viewer like this one on your tablet, install a VNC server on your laptop and off you go ;-)