If you had a magic button on your phone that could do anything what would it do?

Teleport me through time and space.

On a more serious note, I think you're probably trying to do customer development, and trying to modify the question people tell you to ask "If you had a magic wand, what would you improve to solve your problem?"

This can be a useful question if you're already talking about a pretty well defined problem space. So, for example, if you were talking about how people deal with all the photos they take on their phones, the magic wand question might yield you things like "I want an easy way to back them up online".

But the way you're asking it is so open ended that you're essentially saying "What app do you want that doesn't exist", which tends to yield nonsense because there's not a concrete enough frame of reference.

Turn it into a real computer -- i.e. materialize a keyboard, decent-sized monitor, and ethernet port out of the aether.

Put it into self destruction mode, explodes within 30 seconds.

cigarette lighter

extend my light saber ... on my iSaber