I decided to put the innards of my Wacom in an erasable "magic slate" to fix that problem and make the overall experience more touchable and fun. I wired it so that sliding the writing surface of the slate out clears both the slate's screen and the computer drawing program's screen.Then I converted the tablet's outer casing into a watercolor palette.
For the Magic Tablet
1 Wacom or other digital graphics tablet (eBay-ed or old is good, there's a chance of damaging it)
1 magic slate (this one for instance: http://www.amazon.com/Magic-Drawing-Slate-by-Schylling/dp/B000ICZ5IW/ref=sr_1_1?ie=UTF8&s=toys-and-games&qid=1226218291&sr=1-1)
Conductive fabric, copper tape, or aluminum foil
Some wire, solder, and a soldering station
Glue, hot glue, scissors, possibly a utility knife (Wikipedia says this is the proper generic name for an x-acto :)
Bits of cardstock
For the "Digital Watercolor Set"
Outside casing for a Wacom "Bamboo Fun"
Watercolors in tubes
A hot glue gun
A plastic bottled water cap
Step 1: Disassemble tablet
Very carefully pry the casing apart (using a flat screwdriver to gradually pry up the edges helps). If you're using the tablet I did (the Wacom "Bamboo Fun") you can pull out the scroll touchpad from a little plastic slot but BE CAREFUL! I damaged the connections when pulling mine out and ended up breaking the touchpad. Carefully remove the board and the insulating metallic sheet behind it.
I really ought to have more pictures for this step, but I disassembled mine a long time ago. It's pretty straightforward, but let me know if I can offer any assistance.