I've been browsing this fantasic site, and came across Johnny Lee's Wiimote project.
Here's a clip of what he has found:
So I thought I would try building my own Pen and find the items required in Australia.
I have completed my Pen and have also found an easily accessible Bluetooth device.
We use this now at the School I work at, and it is a handy device and inexpensive to build.
We can use it on any whiteboard, wall, Laptop Screen, or external monitor you can think of.
Here's the finished product: