As it turns out, Nokia developed an internet tablet all the way back in 2001. It was called the Nokia M510, several thousand units were made, and it was functional. Sadly, market research showed that consumers were not yet ready for a device like this, and so the project was cancelled. It had a 800x600 display, ran EPOC (Symbian), and sported wifi. The stories are in Finnish, and since I don't speak Finnish, I had to rely on Google Translate (as a translator, this made me feel dirty).
Now that Nokia's devices division is essentially dead, it wouldn't surprise me to see more of these stories to come out. There must be some truly outrageous stuff locked away at Nokia.