Canabalt: Typing Tutor Edition is the same game you're familiar with, but with the jump command mapped to a letter key that changes after every few uses, displayed in the corner of the screen. In order to successfully navigate the endless rooftop path, you have to be able to access the right key immediately. It also includes optional spacebar or double-click-based control options.
You can play the game in a browser window here. We don't expect to see this one on iPhone -- or, at least, we hope we never have to use the iPhone's virtual keyboard for this.