This is way down on the priority list, but it is kinda cool. Differentiator? Especially since you have been promoting the iPad Pro, @Danny.
Allow me to use a pen to annotate in the various browsers, like below. Associate the scribbles with the appropriate items, not with the whole page, so it shows up in various sort orders, filtered views, etc. Album scribbles on albums listed under an artist. Now playing. Etc.