Making OS X features available in iOS
Something that might be useful, that actually is touch oriented. You know, like when you need to go back or forward in browser on OS X, you can just swipe two fingers either direction (depending on which way you want to go in the browser), or one with the Magic Mouse.
For example, on the iPhone or iPod touch, a person can swipe back with one finger to go back, while on the iPad or iPad mini they could use two fingers.
Also, instead of it being a Safari-exclusive feature, make the code available for all alternative browsers on iOS too. Is this just me, or would this not be a kind of nice and useful feature for iOS?