My new Wacom Bamboo One graphics tablet just arrived (£40 GBP from Amazon.co.uk), and after a bit of hassle installing drivers it's working. Even without much practice I notice I can enter characters a lot quicker with this compared to a laptop touchpad (as everyone said I would be able to).
Still a little wobbliness and unrecognised strokes, but I think one important thing is that actually writing characters like you would with a pen seems to be a more natural way to do it. I think this will help memorising, I already feel it's testing a different part of my brain.