I haven't seen anyone doing this yet, so I thought I'd give it a shot:

https://github.com/dppc/p8keyboard.js

It's a total hack, and obviously works only in the context of a browser.

I imagine it as an awkward rubber chiclet keyboard that plugs into the game controller ports.

The demo (arrows to move, spacebar to erase) is for making terminal/typewriter art like this:

Typing is possible, but would need a buffer to hold incoming characters in order to work reliably enough for something like a typing tutor game.

Enjoy!