Singapore-based developer Rockmoon has built a tech demo using the Unity Engine that takes two people to play in true co-op fashion. One player flies the ship using Kinect-based motion controls and the other controls the guns with an iPhone or iPod. The game is merely a proof of concept, and the developers are unsure if anything more will come of it, but it's an interesting use of two completely different technologies working together.
Co-Op technologies for a co-op game? Co-Optacular.