Your phone is typically set to lock its screen after a minute or so of not touching it.
This is really a problem when trying to follow a recipe.

Why not write an app that complements the Flight mode, Movie mode, Meeting mode and Whatnot modes there are, with a Recipe mode.

This Recipe mode, in its simplest solution would just turn of locking and turning off the screen. In a more advanced solution it would lock the screen but let the web page with the recipe still be on and scrollable.