A couple of weeks ago, I learned the term chindogu — an "unuseless" invention, something that theoretically serves a purpose but which one would find too embarrassing to actually use. For example, a T-shirt with a numbered grid on the back which you could use to tell someone exactly where to scratch; or chopsticks with a small electric fan attached, to cool your noodles without having to blow on them.
While searching for more info on the Nokia 770, I came across this, and I'm not sure whether it's useful or unuseless: a combination cellphone/glucose meter.