According to Griffin McElroy at Polygon, the on-board air hockey game that comes installed as part of the PS4's PlayRoom demo (seen at 0:55 above) is actually really cool:
At face value, it's not especially exciting — it's the way you can manipulate the court that puts an interesting spin on things.
Both players can twist their controllers to twist their end of the table up or down, letting you contort the playing field in any number of ways. By moving your light bar closer to your opponents, the field shrinks in response — the inverse is true too, as moving away from your opponent can stretch the table out to enormous lengths.
Basically, it's pong, if you could physically bend your old monochrome TV with your mind.