Well, I finally got something that could be called a graphics tablet. It involves a wii remote, a cheap bluetooth dongle and a lot of luck.
Basically the idea is to have a pen type device that is equipped with an IR LED. The wii remote is placed in a fixed position and detects the IR light reflecting on the monitor, and various programs translate the data sent through the dongle into SAI.
However, I realized that I had lost my IR LED, and instead used the remote for my iPod dock as a pen. And because I didn't have anywhere to put the wiimote, I had it 8 feet away from the monitor (should have been 2-3 feet). In my profile picture, it was sitting on the top shelf behind me. So the wiimote was looking in a tiny area for an LED that was partially covered - meaning its accuracy was terrible.
I managed to draw a very lovely series of blueish dots on my monitor. Already my art skills have improved!