Instead of the boring words-per-minute (wpm) rating when talking about typing speed, how about going by revolutions per minute (rpm)? Seen here is the USB Mice Wheel (that's the product name, though there's only one mouse there), which responds to your typing speed. The faster you go, the faster it turns.
The product requires you to install some software, and it works only for Windows XP. If you'd rather not plug it in, you can put in some batteries and it'll still work, except the speed will be controlled by a knob and not your keyboard. From the product page, the company making it appears to be a Chinese manufacturer that sells in bulk, so it should probably appear on online novelty shops after a while. We'll definitely be keeping this away from our 120wpm colleague--she'll probably run the mouse till it dies.
(Via Crave Asia)