Typyst app for iPhone and iPad
Typyst faithfully recreates the experience of hearing every nuance of an authentic set of typewriters using your keyboard. The sounds were recorded in the same environment you would actually use a typewriter and edited to sound amazing in earbuds, over a pair of desktop speakers or even in a world-class studio. Also provides metrics on your typing speed and consistency.
Currently offering the sounds of the Olympia SM3, Royal Model-P and Smith-Corona Silent models.