A second monitor for your Mac, when you're on your Grownup Computer: That's a perfect use for the 1024x768 iPad, and exactly what some apps (You can search relational apps by the google) iDisplay lets you do.
The concept and execution are equally simple: Your iPad serves as a secondary display for your Mac (and only your Mac), by leveraging a transparent VNC server and an artificial second monitor. Run the server app on your computer, run the client app on your iPad, arrange the displays in your OS X settings, and you've got an instant second monitor.