I bet there's a market for a truly adaptive mobile keyboard. It could track when you go back and correct typos and learn over time where the user's fingers expect to find the keys, then put those keys there as well as manipulating their size and shape for maximum accuracy. For example, I often hit the spacebar when I'm trying to thumb the N key, so it could move the spacebar further away from the rest of the keys or even retract the section of it near that key.