After our kid was born, I did a lot of little personal programming projects on my phone, in the small of the night, with baby sleeping on me or drinking a bottle. This experience convinced me that programming on a phone is perfectly viable, and that all the existing options are terrible. It’s not rocket science, programming has a small vocabulary: keywords, numbers, and in-scope variables. A keyboard interface that presents these options could be as fast or faster than programming on a computer.