So what's the kicker? Well, as you progress through the iOS game you unlock various parts of items, just as you do in the PS4 game. Find all the constituent parts and you unlock that item, which you'll then be able to "send" to Knack in the PS4 game itself. That functionality isn't built into the iOS game yet, not that it'd be much use without the console or its game.
As for the PS4 game, I enjoyed my time at E3 with Mark Cerny's action-adventure. Much like its iOS sibling, I found it pretty easy to get the knack of Knack, and it should be one of the more accessible PS4 launch games, albeit on the lower difficulties.
Knack is one of 17 games confirmed for to be available when the PS4 launches next week on November 15, with the console priced at $400.