I love this concept! I found myself just playing with it for awhile. It would be really fun as a phone game. It looks like you've already addressed it but I think the switch to 741/963 and qaz/edc will make a huge difference on the playability on the keyboard.
I did have some issues seeing some of the numbers clearly, maybe if you could make the font thicker or the background contrast different it would be easier. I was also wondering if you've considered the option to change the colors for color blind players.