I created an enhanced multilingual T9 keyboard[1][2] for iOS in 2014 to play around with Swift. It's been doing 600$ on average since then, still going strong. Still use it everyday myself and can't live without it [1] https://itunes.apple.com/us/app/typenine-ultimate-t9-style-k... [2] https://medium.com/porsager/a-better-iphone-typing-experienc...