Ok this is something which I made, that I thought would be useful to me. So, I thought I would share my ideas.
I have been teaching for a short while now, and it occured to me that I could make my own Interactive Whiteboard as a practice tool at home. I feel my end product is much more than that. If you used a laptop with a digital projector, you pretty much have a good sized standard Interactive Whiteboard to use anywhere. The only difference is that the commercial models cost several thousands, and our ghetto whiteboard costs umm... about £20/$40.
So this is what we need:

-1 Nintendo Wii remote/Wiimote . Which I bought on ebay for around £15/$30.
-1 Bluetooth Dongle. Again, from ebay for £3/$6

and
-1 homemade/DIY IR pen

For the pen you need:

-1 empty plastic biro pen tube
-1 AAA battery
-1 AAA battery holder - around 40 pence
-1 push-to-engage microswitch - around 80 pence
-1 100ma Infra Red (IR) LED - around 70 pence
-Some thin plastic coated wire
-Some tape
You can get all the electrical components you need from Maplin.

If you have a soldering iron too, then whoop-dee-doo.

When putting the pen together, I like to listen to Raffi songs.

For the software:
-SMART Notepad software
-Bluetooth application (Like Bluesoleil)
-This Wii whiteboard Calibration Application
-Microsoft .Net Framework
-Direct X SDK

Position your Wiimote like facing your screen like this:

Then connect the Wiimote to your Bluetooth dongle using Bluesoleil software:

Once connected, run the Wiimote Whiteboard calibration app. And using your IR pen, click once on each of the four crosshairs on the screen. This enables the Wiimote to recognise the boundary of your computer screen.

Then, Launch the SMART notebook application:

And scribble away. The pen is engaged with the click of the microswitch. You can select the various writing tools, and board rubbers. Even play interactive educational activities like those found on the BBCinteractive website!! If you have any questions then just ask me. :)